How to validate an email address using a regular expression

Question

Over the years I have slowly developed a regular expression that validates MOST email addresses correctly  assuming they don t use an IP address as the server part   I use it in several PHP programs  and it works most of the time   However  from time to time I get contacted by someone that is having trouble with a site that uses it  and I end up having to make some adjustment  most recently I realized that I wasn t allowing 4-character TLDs    What is the best regular expression you have or have seen for validating emails   I ve seen several solutions that use functions that use several shorter expressions  but I d rather have one long complex expression in a simple function instead of several short expression in a more complex function

User · Answer

I always use the below regular expression to validate the email address. This is the best regex I have ever seen to validate email address.

"\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\Z";

This regular expression I always uses in my Asp.NET Code and I'm pretty satisfied with it.

use this assembly reference

using System.Text.RegularExpressions;

and try the following code, as it is simple and do the work for you.

private bool IsValidEmail(string email) {
    bool isValid = false;
    const string pattern = @"\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\Z";

    isValid = email != "" && Regex.IsMatch(email, pattern);

    // an alternative of the above line is also given and commented
    //
    //if (email == "") {
    //    isValid = false;
    //} else {
    //    // address provided so use the IsMatch Method
    //    // of the Regular Expression object
    //    isValid = Regex.IsMatch(email, pattern);
    //}
    return isValid;
}

this function validates the email string. If the email string is null, it returns false, if the email string is not in a correct format it returns false. It only returns true if the format of the email is valid.

User · Answer

I found nice article  which says that the best way to validate e-mail address is that regex expresion              i

User · Answer

For me the right way for checking emails is    Check that symbol   exists  and before and after it there are some non-  symbols                   Try to send an email to this address with some  activation code   When the user  activated  his email address  we will see that all is right    Of course  you can show some warning or tooltip in front-end when user typed  strange  email to help him to avoid common mistakes  like no dot in domain part or spaces in name without quoting and so on  But you must accept the address  hello world  if user really want it   Also  you must remember that email address standard was and can evolute  so you can t just type some  standard-valid  regexp once and for all times  And you must remember that some concrete internet servers can fail some details of common standard and in fact work with own  modified standard    So  just check    hint user on frontend and send verification emails on given address

User · Answer

Although very detailed answers are already added  I think those are complex enough for a developer who is just looking for a simple method to validate an Email address or to get all Email Address From string in java   public static boolean isEmailValid  NonNull String email            return android util Patterns EMAIL ADDRESS matcher email  matches            As per the regular expression is concerned  I always use this regular expression  which works for my problems     A-Z0-9a-z    -    A-Za-z0-9 -     A-Za-z  2 6     If you are looking to find all email addresses from a String by matching email Regular Expression  You can find a method at this link

User · Answer

I would not suggest to use an regex at all - email addresses are way too complicated for that  This is a common problem so I would guess there are many libraries that contain a validator - if you use Java the EmailValidator of apache commons validator is a good one

User · Answer

email regex  RFC5322     im       1 64                                       0-9a-z              -      amp                     w      0-9a-z         1 255             d 1 3     3  d 1 3              1 63     0-9a-z  - w   0-9a-z       a-z0-9   -a-z0-9  0 22  a-z0-9         1 63    0-9a-z  - w        Demo https   regex101 com r ObS3QZ 1        im       1 64                                       0-9a-z              -      amp                     w      0-9a-z         1 255             d 1 3     3  d 1 3              1 63     0-9a-z  - w   0-9a-z       a-z0-9   -a-z0-9  0 22  a-z0-9         1 63    0-9a-z  - w          Note - remove all comments   comments   before runninig this regex    Find             replace with nothing     im                                        Case insensitive                                              BOS                                               Local part        1 64                                  64 max chars                                                         1 start   Quoted                                                                                                                                   1 end                                                  or                                                      2 start   Non-quoted                                 0-9a-z                                                                                                                                            or                         -      amp                     w                                                0-9a-z                                                                   2 end                                                  Domain part        1 255                                 255 max chars                                                         3 start   IP                               d 1 3       3              d 1 3                                                        3 end                                                  or                                                        4 start   Others                                                        Labels  63 max chars each                        1 63                        0-9a-z   - w    0-9a-z                                                 a-z0-9    -a-z0-9  0 22   a-z0-9                                                      4 end                                                  or                                                     5 start   Localdomain                  1 63                  0-9a-z   - w                                                       5 end                                                  EOS

User · Answer

I use    w   -     w     w   -   w      w   -   w       Which is the one used in ASP NET by the RegularExpressionValidator

User · Answer

World s most popular blogging platform WordPress uses this function to validate email address    But they are doing it with multiple steps     You don t have to worry anymore when using the regex mentioned in this function     Here is the function            Verifies that an email is valid        Does not grok i18n domains  Not RFC compliant         since 0 71        param string  email Email address to verify      param boolean  deprecated Deprecated      return string bool Either false or the valid email address      function is email   email   deprecated   false         if     empty   deprecated              deprecated argument    FUNCTION     3 0             Test for the minimum length the email can be     if   strlen   email    lt  3             return apply filters   is email   false   email   email too short                   Test for an   character after the first position     if   strpos   email       1       false             return apply filters   is email   false   email   email no at                   Split out the local and domain parts     list   local   domain     explode        email  2            LOCAL PART        Test for invalid characters     if    preg match      a-zA-Z0-9     amp                  -        local               return apply filters   is email   false   email   local invalid chars                   DOMAIN PART        Test for sequences of periods     if   preg match       2       domain               return apply filters   is email   false   email   domain period sequence                   Test for leading and trailing periods and whitespace     if   trim   domain     t n r 0 x0B          domain             return apply filters   is email   false   email   domain period limits                   Split the domain into subs      subs   explode        domain            Assume the domain will have at least two subs     if   2  gt  count   subs               return apply filters   is email   false   email   domain no periods                   Loop through each sub     foreach    subs as  sub                Test for leading and trailing hyphens and whitespace         if   trim   sub     t n r 0 x0B-         sub                 return apply filters   is email   false   email   sub hyphen limits                           Test for invalid characters         if    preg match     a-z0-9-    i    sub                   return apply filters   is email   false   email   sub invalid chars                             Congratulations your email made it      return apply filters   is email    email   email  null

User · Answer

The regular expressions posted in this thread are out of date now because of the new generic top level domains  gTLDs  coming in  e g   london   basketball        To validate an email address there are two answers  That would be relevant to the vast majority     As the main answer says - don t use a regular expression  just validate it by sending an email to the address  Catch exceptions for invalid addresses  Use a very generic regex to at least make sure that they are using an email structure  something   something   something   There s no point in going for a detailed regex because you won t catch them all and there ll be a new batch in a few years and you ll have to update your regular expression again    I have decided to use the regular expression because  unfortunately  some users don t read forms and put the wrong data in the wrong fields  This will at least alert them when they try to put something which isn t an email into the email input field and should save you some time supporting users on email issues             2         2

User · Answer

The email addresses I want to validate are going to be used by an ASP NET web application using the System Net Mail namespace to send emails to a list of people   So  rather than using some very complex regular expression  I just try to create a MailAddress instance from the address  The MailAddress constructor will throw an exception if the address is not formed properly  This way  I know I can at least get the email out of the door  Of course this is server-side validation  but at a minimum you need that anyway   protected void emailValidator ServerValidate object source  ServerValidateEventArgs args        try               var a   new MailAddress txtEmail Text             catch  Exception ex                args IsValid   false          emailValidator ErrorMessage    email      ex Message

User · Answer

a-zA-Z0-9-       a-zA-Z0-9-      a-zA-Z0-9-      a-zA-Z0-9-         0-9  1 3     a-zA-Z  2 3    aero coop info museum name      This matches 99 99  of email addresses  including some of the newer top-level-domain extensions  such as info  museum  name  etc   It also allows for emails tied directly to IP addresses

User · Answer

I use this         lt  gt              s          lt  gt              s                     0-9  1 3    0-9  1 3    0-9  1 3    0-9  1 3       a-zA-Z -0-9       a-zA-Z  2

User · Answer

The fully RFC 822 compliant regex is inefficient and obscure because of its length   Fortunately  RFC 822 was superseded twice and the current specification for email addresses is RFC 5322   RFC 5322 leads to a regex that can be understood if studied for a few minutes and is efficient enough for actual use   One RFC 5322 compliant regex can be found at the top of the page at http   emailregex com  but uses the IP address pattern that is floating around the internet with a bug that allows 00 for any of the unsigned byte decimal values in a dot-delimited address  which is illegal   The rest of it appears to be consistent with the RFC 5322 grammar and passes several tests using grep -Po  including cases domain names  IP addresses  bad ones  and account names with and without quotes   Correcting the 00 bug in the IP pattern  we obtain a working and fairly fast regex    Scrape the rendered version  not the markdown  for actual code           a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9             2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9       3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          or       a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9             2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9       3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          Here is diagram of finite state machine for above regexp which is more clear than regexp itself   The more sophisticated patterns in Perl and PCRE  regex library used e g  in PHP  can correctly parse RFC 5322 without a hitch  Python and C  can do that too  but they use a different syntax from those first two  However  if you are forced to use one of the many less powerful pattern-matching languages  then it   s best to use a real parser   It s also important to understand that validating it per the RFC tells you absolutely nothing about whether that address actually exists at the supplied domain  or whether the person entering the address is its true owner  People sign others up to mailing lists this way all the time  Fixing that requires a fancier kind of validation that involves sending that address a message that includes a confirmation token meant to be entered on the same web page as was the address    Confirmation tokens are the only way to know you got the address of the person entering it  This is why most mailing lists now use that mechanism to confirm sign-ups  After all  anybody can put down president whitehouse gov  and that will even parse as legal  but it isn t likely to be the person at the other end   For PHP  you should not use the pattern given in Validate an E-Mail Address with PHP  the Right Way from which I quote      There is some danger that common usage and widespread sloppy coding will establish a de facto standard for e-mail addresses that is more restrictive than the recorded formal standard    That is no better than all the other non-RFC patterns  It isn   t even smart enough to handle even RFC 822  let alone RFC 5322  This one  however  is   If you want to get fancy and pedantic  implement a complete state engine  A regular expression can only act as a rudimentary filter  The problem with regular expressions is that telling someone that their perfectly valid e-mail address is invalid  a false positive  because your regular expression can t handle it is just rude and impolite from the user s perspective  A state engine for the purpose can both validate and even correct e-mail addresses that would otherwise be considered invalid as it disassembles the e-mail address according to each RFC  This allows for a potentially more pleasing experience  like     The specified e-mail address  myemail address com  is invalid  Did you mean  myemail address com     See also Validating Email Addresses  including the comments  Or Comparing E-mail Address Validating Regular Expressions     Debuggex Demo

User · Answer

The email addresses I want to validate are going to be used by an ASP NET web application using the System Net Mail namespace to send emails to a list of people   So  rather than using some very complex regular expression  I just try to create a MailAddress instance from the address  The MailAddress constructor will throw an exception if the address is not formed properly  This way  I know I can at least get the email out of the door  Of course this is server-side validation  but at a minimum you need that anyway   protected void emailValidator ServerValidate object source  ServerValidateEventArgs args        try               var a   new MailAddress txtEmail Text             catch  Exception ex                args IsValid   false          emailValidator ErrorMessage    email      ex Message

User · Answer

Per the W3C HTML5 spec     a-zA-Z0-9      amp              -    a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9         a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9         Context      A valid e-mail address is a string that matches the ABNF production             Note  This requirement is a willful violation of RFC 5322  which defines a syntax for e-mail addresses that is simultaneously too strict  before the         character   too vague  after the         character   and too lax  allowing comments  whitespace characters  and quoted strings in manners unfamiliar to most users  to be of practical use here       The following JavaScript- and Perl-compatible regular expression is an implementation of the above definition          a-zA-Z0-9      amp              -    a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9         a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9

User · Answer

In order to validate an email address with JavaScript it is more convenient and efficient use this function  according with w3school    function validateEmail     var x document f email value  var atpos x indexOf       var dotpos x lastIndexOf       if  atpos lt 1    dotpos lt atpos 2    dotpos 2 gt  x length          alert  Not a valid e-mail address       return false           I use it and it s perfect  I hope to be useful

User · Answer

public bool ValidateEmail string sEmail        if  sEmail    null                return false             int nFirstAT   sEmail IndexOf           int nLastAT   sEmail LastIndexOf            if   nFirstAT  gt  0   amp  amp   nLastAT    nFirstAT   amp  amp   nFirstAT  lt   sEmail Length - 1                  return  Regex IsMatch sEmail      a-z 0-9 A-Z       a-z 0-9 A-Z         a-z 0-9 A-Z         a-z 0-9 A-Z          a-z 0-9 A-Z        a-z  a-z 0-9 A-Z      a-z  a-z 0-9 A-Z      a-z  a-z 0-9 A-Z                     else               return false

User · Answer

This rule matches what our postfix server could not send to   allow letters  numbers  -            amp         no -foo bar com  no asd -bar com      a-z0-9        amp    -a-z0-9        amp         a-z0-9  -a-z0-9       -a-z0-9       a-z  2     i

User · Answer

It all depends on how accurate you want to be   For my purposes  where I m just trying to keep out things like bob   aol com  spaces in emails  or steve  no domain at all  or mary aolcom  no period before  com   I use     S   S    S      Sure  it will match things that aren t valid email addresses  but it s a matter of getting common simple errors   There are any number of changes that can be made to that regex  and some are in the comments for this answer   but it s simple  and easy to understand  and is a fine first attempt

User · Answer

You could use the one employed by the jQuery Validation plugin         a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF        a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x22      x20  x09    x0d x0a     x20  x09        x01- x08 x0b x0c x0e- x1f x7f   x21   x23- x5b    x5d- x7e    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF         x01- x09 x0b x0c x0d- x7f    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x20  x09    x0d x0a     x20  x09      x22        a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF           a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF         i

User · Answer

Quick answer  Use the following regex for input validation     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -         0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       Addresses matched by this regex    have a local part  i e  the part before the  -sign  that is strictly compliant with RFC 5321 5322  have a domain part  i e  the part after the  -sign  that is a host name with at least two labels  each of which is at most 63 characters long    The second constraint is a restriction on RFC 5321 5322   Elaborate answer  Using a regular expression that recognizes email addresses could be useful in various situations  for example to scan for email addresses in a document  to validate user input  or as an integrity constraint on a data repository   It should however be noted that if you want to find out if the address actually refers to an existing mailbox  there s no substitute for sending a message to the address  If you only want to check if an address is grammatically correct then you could use a regular expression  but note that       is a grammatically correct email address that certainly doesn t refer to an existing mailbox   The syntax of email addresses has been defined in various RFCs  most notably RFC 822 and RFC 5322  RFC 822 should be seen as the  original  standard and RFC 5322 as the latest standard  The syntax defined in RFC 822 is the most lenient and subsequent standards have restricted the syntax further and further  where newer systems or services should recognize obsolete syntax  but never produce it   In this answer I   ll take    email address    to mean addr-spec as defined in the RFCs  i e  jdoe example org  but not  John Doe  lt jdoe example org gt   nor some-group jdoe example org mrx exampel org     There s one problem with translating the RFC syntaxes into regexes  the syntaxes are not regular  This is because they allow for optional comments in email addresses that can be infinitely nested  while infinite nesting can t be described by a regular expression  To scan for or validate addresses containing comments you need a parser or more powerful expressions   Note that languages like Perl have constructs to describe context free grammars in a regex-like way   In this answer I ll disregard comments and only consider proper regular expressions   The RFCs define syntaxes for email messages  not for email addresses as such  Addresses may appear in various header fields and this is where they are primarily defined  When they appear in header fields addresses may contain  between lexical tokens  whitespace  comments and even linebreaks  Semantically this has no significance however  By removing this whitespace  etc  from an address you get a semantically equivalent canonical representation  Thus  the canonical representation of first  last  comment       3 5 7 9  is first last  3 5 7 9    Different syntaxes should be used for different purposes  If you want to scan for email addresses in a  possibly very old  document it may be a good idea to use the syntax as defined in RFC 822  On the other hand  if you want to validate user input you may want to use the syntax as defined in RFC 5322  probably only accepting canonical representations  You should decide which syntax applies to your specific case   I use POSIX  extended  regular expressions in this answer  assuming an ASCII compatible character set   RFC 822  I arrived at the following regular expression  I invite everyone to try and break it  If you find any false positives or false negatives  please post them in a comment and I ll try to fix the expression as soon as possible           lt  gt           x00- x1F x7F      n     r         r n       r        r               lt  gt           x00- x1F x7F      n     r         r n       r        r               lt  gt           x00- x1F x7F       n     r          r n       r        r               lt  gt           x00- x1F x7F       n     r          r n       r        r        I believe it s fully complient with RFC 822 including the errata  It only recognizes email addresses in their canonical form  For a regex that recognizes  folding  whitespace see the derivation below   The derivation shows how I arrived at the expression  I list all the relevant grammar rules from the RFC exactly as they appear  followed by the corresponding regex  Where an erratum has been published I give a separate expression for the corrected grammar rule  marked  erratum   and use the updated version as a subexpression in subsequent regular expressions   As stated in paragraph 3 1 4  of RFC 822 optional linear white space may be inserted between lexical tokens  Where applicable I ve expanded the expressions to accommodate this rule and marked the result with  opt-lwsp    CHAR            lt any ASCII character gt                    CTL             lt any ASCII control character and DEL gt                   x00- x1F x7F   CR              lt ASCII CR  carriage return gt                  r  LF              lt ASCII LF  linefeed gt                  n  SPACE           lt ASCII SP  space gt                    HTAB            lt ASCII HT  horizontal-tab gt                  t   lt   gt              lt ASCII quote mark gt                    CRLF           CR LF                 r n  LWSP-char      SPACE   HTAB                   t   linear-white-space    1   CRLF  LWSP-char                           r n     t     specials                     lt       gt                                     lt   gt                                          lt  gt            quoted-pair        CHAR                     qtext           lt any CHAR excepting  lt   gt        amp  CR  and including linear-white-space gt                       r     r n     t     dtext           lt any CHAR excluding                amp  CR   amp  including linear-white-space gt                        r     r n     t     quoted-string      lt   gt    qtext quoted-pair   lt   gt                            r     r n     t           erratum             n     r         r n       r    r n     t        r     domain-literal          dtext quoted-pair                                  r     r n     t           erratum              n     r          r n       r    r n     t        r     atom           1  lt any CHAR except specials  SPACE and CTLs gt                        lt  gt           x00- x1F x7F    word           atom   quoted-string                       lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r     domain-ref     atom  sub-domain     domain-ref   domain-literal                       lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r     local-part     word       word                         lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r               lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r        opt-lwsp              lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r        r n     t        r n     t           lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r        domain         sub-domain       sub-domain                         lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r               lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        opt-lwsp              lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        r n     t        r n     t           lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        addr-spec      local-part     domain                        lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r               lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r               lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r               lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        opt-lwsp              lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r       r n     t         r n     t           lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r       r n     t         r n     t           lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        r n     t        r n     t           lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        canonical             lt  gt           x00- x1F x7F      n     r         r n       r        r               lt  gt           x00- x1F x7F      n     r         r n       r        r               lt  gt           x00- x1F x7F       n     r          r n       r        r               lt  gt           x00- x1F x7F       n     r          r n       r        r         RFC 5322  I arrived at the following regular expression  I invite everyone to try and break it  If you find any false positives or false negatives  please post them in a comment and I ll try to fix the expression as soon as possible     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          -  -    -9  A-Z -       -  -    -9  A-Z -          t -Z -       I believe it s fully complient with RFC 5322 including the errata  It only recognizes email addresses in their canonical form  For a regex that recognizes  folding  whitespace see the derivation below   The derivation shows how I arrived at the expression  I list all the relevant grammar rules from the RFC exactly as they appear  followed by the corresponding regex  For rules that include semantically irrelevant  folding  whitespace  I give a separate regex marked   normalized   that doesn t accept this whitespace   I ignored all the  obs-  rules from the RFC  This means that the regexes only match email addresses that are strictly RFC 5322 compliant  If you have to match  old  addresses  as the looser grammar including the  obs-  rules does   you can use one of the RFC 822 regexes from the previous paragraph   VCHAR                x21-7E                       -    ALPHA                x41-5A    x61-7A                      A-Za-z   DIGIT                x30-39                      0-9   HTAB                 x09                      t  CR                   x0D                      r  LF                   x0A                      n  SP                   x20                       DQUOTE               x22                        CRLF                CR LF                      r n  WSP                 SP   HTAB                       t    quoted-pair              VCHAR   WSP                          t -    FWS                    WSP CRLF  1 WSP                         t    r n    t     ctext                d33-39    d42-91    d93-126                        -  -  -      comment  is left out in the regex  ccontent            ctext   quoted-pair   comment                        -  -  -        t -      not regular  comment                    FWS  ccontent   FWS        is equivalent to FWS when leaving out comments  CFWS                 1   FWS  comment   FWS     FWS                        t    r n    t     atext               ALPHA   DIGIT                             amp                        -                                                                                   -  -    -9  A-Z -    dot-atom-text       1 atext       1 atext                       -  -    -9  A-Z -       -  -    -9  A-Z -       dot-atom             CFWS  dot-atom-text  CFWS                          t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t       normalized          -  -    -9  A-Z -       -  -    -9  A-Z -       qtext                d33    d35-91    d93-126                         -  -    qcontent            qtext   quoted-pair                         -  -        t -      erratum  quoted-string        CFWS  DQUOTE   1   FWS  qcontent   FWS     FWS  DQUOTE  CFWS                          t    r n    t            t    r n    t          -  -        t -          t    r n    t          t    r n    t           t    r n    t       normalized               -  -   t       t -        dtext                d33-90    d94-126                       -Z -    domain-literal       CFWS         FWS  dtext   FWS       CFWS                          t    r n    t            t    r n    t       -Z -        t    r n    t          t    r n    t       normalized             t -Z -      local-part          dot-atom   quoted-string                         t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t          t    r n    t            t    r n    t          -  -        t -          t    r n    t          t    r n    t           t    r n    t       normalized          -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -        domain              dot-atom   domain-literal                         t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t          t    r n    t            t    r n    t       -Z -        t    r n    t          t    r n    t       normalized          -  -    -9  A-Z -       -  -    -9  A-Z -          t -Z -      addr-spec           local-part     domain                          t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t          t    r n    t            t    r n    t          -  -        t -          t    r n    t          t    r n    t           t    r n    t            t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t          t    r n    t            t    r n    t       -Z -        t    r n    t          t    r n    t        normalized           -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          -  -    -9  A-Z -       -  -    -9  A-Z -          t -Z -        Note that some sources  notably w3c  claim that RFC 5322 is too strict on the local part  i e  the part before the  -sign   This is because        a  b  and  a   are not valid dot-atoms  while they may be used as mailbox names  The RFC  however  does allow for local parts like these  except that they have to be quoted  So instead of a  b example net you should write  a  b  example net  which is semantically equivalent   Further restrictions  SMTP  as defined in RFC 5321  further restricts the set of valid email addresses  or actually  mailbox names   It seems reasonable to impose this stricter grammar  so that the matched email address can actually be used to send an email   RFC 5321 basically leaves alone the  local  part  i e  the part before the  -sign   but is stricter on the domain part  i e  the part after the  -sign   It allows only host names in place of dot-atoms and address literals in place of domain literals   The grammar presented in RFC 5321 is too lenient when it comes to both host names and IP addresses  I took the liberty of  correcting  the rules in question  using this draft and RFC 1034 as guidelines  Here s the resulting regex     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z          25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3  IPv6     0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3           IPv6   0-9A-Za-z-   0-9A-Za-z    -Z -        Note that depending on the use case you may not want to allow for a  General-address-literal  in your regex  Also note that I used a negative lookahead    IPv6   in the final regex to prevent the  General-address-literal  part to match malformed IPv6 addresses  Some regex processors don t support negative lookahead  Remove the substring     IPv6   0-9A-Za-z-   0-9A-Za-z    -Z -    from the regex if you want to take the whole  General-address-literal  part out   Here s the derivation   Let-dig             ALPHA   DIGIT                      0-9A-Za-z   Ldh-str                ALPHA   DIGIT    -    Let-dig                      0-9A-Za-z-   0-9A-Za-z    regex is updated to make sure sub-domains are max  63 charactes long - RFC 1034 section 3 5  sub-domain          Let-dig  Ldh-str                       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z     Domain              sub-domain       sub-domain                       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       Snum                1 3DIGIT                      0-9  1 3    suggested replacement for  Snum   ip4-octet           DIGIT    x31-39 DIGIT    1  2DIGIT    2   x30-34 DIGIT    25   x30-35                     25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9   IPv4-address-literal        Snum 3      Snum                               0-9  1 3     0-9  1 3   3    suggested replacement for  IPv4-address-literal   ip4-address         ip4-octet 3     ip4-octet                       25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3    suggested replacement for  IPv6-hex   ip6-h16              0        x49-57    x65-70   x97-102  0 3  x48-57    x65-70   x97-102                        0  1-9A-Fa-f  0-9A-Fa-f  0 3    not from RFC  ls32                ip6-h16     ip6-h16   ip4-address                      0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3    suggested replacement of  IPv6-addr   ip6-address                                            6 ip6-h16      ls32                                                        5 ip6-h16      ls32                                         ip6-h16        4 ip6-h16      ls32                          1 ip6-h16      ip6-h16        3 ip6-h16      ls32                          2 ip6-h16      ip6-h16        2 ip6-h16      ls32                          3 ip6-h16      ip6-h16          ip6-h16      ls32                          4 ip6-h16      ip6-h16                       ls32                          5 ip6-h16      ip6-h16          ip6-h16                          6 ip6-h16      ip6-h16                               0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3        IPv6-address-literal         IPv6   ip6-address                             IPv6     0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3         Standardized-tag            Ldh-str                              0-9A-Za-z-   0-9A-Za-z   dcontent             d33-90    d94-126                       -Z -    General-address-literal     Standardized-tag     1 dcontent                              0-9A-Za-z-   0-9A-Za-z    -Z -     address-literal           IPv4-address-literal   IPv6-address-literal   General-address-literal                               25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3  IPv6     0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3           IPv6   0-9A-Za-z-   0-9A-Za-z    -Z -       Mailbox             Local-part       Domain   address-literal                         -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z          25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3  IPv6     0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3           IPv6   0-9A-Za-z-   0-9A-Za-z    -Z -         User input validation  A common use case is user input validation  for example on an html form  In that case it s usually reasonable to preclude address-literals and to require at least two labels in the hostname  Taking the improved RFC 5321 regex from the previous section as a basis  the resulting expression would be     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -         0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       I do not recommend restricting the local part further  e g  by precluding quoted strings  since we don t know what kind of mailbox names some hosts allow  like  a  b  example net or even  a b  example net    I also do not recommend explicitly validating against a list of literal top-level domains or even imposing length-constraints  remember how   museum  invalidated  a-z  2 4    but if you must     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z        net org com info etc      Make sure to keep your regex up-to-date if you decide to go down the path of explicit top-level domain validation   Further considerations  When only accepting host names in the domain part  after the  -sign   the regexes above accept only labels with at most 63 characters  as they should  However  they don t enforce the fact that the entire host name must be at most 253 characters long  including the dots   Although this constraint is strictly speaking still regular  it s not feasible to make a regex that incorporates this rule   Another consideration  especially when using the regexes for input validation  is feedback to the user  If a user enters an incorrect address  it would be nice to give a little more feedback than a simple  syntactically incorrect address   With  vanilla  regexes this is not possible   These two considerations could be addressed by parsing the address  The extra length constraint on host names could in some cases also be addressed by using an extra regex that checks it  and matching the address against both expressions   None of the regexes in this answer are optimized for performance  If performance is an issue  you should see if  and how  the regex of your choice can be optimized

User · Answer

As mentioned already  you can t validate an email with a regex  However  here s what we currently use to make sure user-input isn t totally bogus  forgetting the TLD etc     This regex will allow IDN domains and special characters  like Umlauts  before and after the   sign       w  -          w -      w-  2 63   iu

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Valid RegEx according to w3 org and wikipedia   A-Z0-9a-z      amp    -              A-Za-z0-9 -      A-Za-z  2 4    e g       amp    -            example com

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email regex  RFC5322     im       1 64                                       0-9a-z              -      amp                     w      0-9a-z         1 255             d 1 3     3  d 1 3              1 63     0-9a-z  - w   0-9a-z       a-z0-9   -a-z0-9  0 22  a-z0-9         1 63    0-9a-z  - w        Demo https   regex101 com r ObS3QZ 1        im       1 64                                       0-9a-z              -      amp                     w      0-9a-z         1 255             d 1 3     3  d 1 3              1 63     0-9a-z  - w   0-9a-z       a-z0-9   -a-z0-9  0 22  a-z0-9         1 63    0-9a-z  - w          Note - remove all comments   comments   before runninig this regex    Find             replace with nothing     im                                        Case insensitive                                              BOS                                               Local part        1 64                                  64 max chars                                                         1 start   Quoted                                                                                                                                   1 end                                                  or                                                      2 start   Non-quoted                                 0-9a-z                                                                                                                                            or                         -      amp                     w                                                0-9a-z                                                                   2 end                                                  Domain part        1 255                                 255 max chars                                                         3 start   IP                               d 1 3       3              d 1 3                                                        3 end                                                  or                                                        4 start   Others                                                        Labels  63 max chars each                        1 63                        0-9a-z   - w    0-9a-z                                                 a-z0-9    -a-z0-9  0 22   a-z0-9                                                      4 end                                                  or                                                     5 start   Localdomain                  1 63                  0-9a-z   - w                                                       5 end                                                  EOS

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Had to mention  that nearly has been added new domain  yandex   Possible emails  test job yandex  And also uppercase letters supported  so a bit modified version of acrosman solution is      a-zA-Z0-9-       a-zA-Z0-9-      a-zA-Z0-9-      a-zA-Z0-9-        a-zA-Z  2 6

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Strange that you  cannot  allow 4 characters TLDs   You are banning people from  info and  name  and the length limitation stop  travel and  museum  but yes  they are less common than 2 characters TLDs and 3 characters TLDs   You should allow uppercase alphabets too   Email systems will normalize the local part and domain part   For your regex of domain part  domain name cannot starts with  -  and cannot ends with  -   Dash can only stays in between   If you used the PEAR library  check out their mail function  forgot the exact name library    You can validate email address by calling one function  and it validates the email address according to definition in RFC822

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This regex is from Perl s Email  Valid library  I believe it to be the most accurate  it matches all 822  And  it is based on the regular expression in the O Reilly book      Regular expression built using Jeffrey Friedl s example in   Mastering Regular Expressions  http   www ora com catalog regexp       RFC822PAT    lt  lt  EOF     040 t            x80- xff n 015               x80- xff         x80-  xff n 015            x80- xff      x80- xff n 015              x80- xf f n 015          040 t              040  lt  gt              000- 037 x80- x ff         040  lt  gt              000- 037 x80- xff         x80- xff n 015            x80- xff      x80- xff n 015         040 t            x80-  xff n 015               x80- xff         x80- xff n 015            x80 - xff      x80- xff n 015              x80- xff n 015          040 t            040 t            x80- xff n 015               x80- xff          x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040  lt  gt              000- 037 x8 0- xff         040  lt  gt              000- 037 x80- xff         x80- xff n  015           x80- xff      x80- xff n 015         040 t            x 80- xff n 015               x80- xff         x80- xff n 015             x80- xff      x80- xff n 015              x80- xff n 015          040  t         040 t            x80- xff n 015               x80- xff          x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040  lt  gt              000- 037  x80- xff         040  lt  gt              000- 037 x80- xff             x80-  xff n 015           x80- xff        040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff       x80- xff n 015              x80- xff n 015          040 t           04 0 t            x80- xff n 015               x80- xff         x80- xff  n 015            x80- xff      x80- xff n 015              x80- xff n  015          040 t           040  lt  gt              000- 037 x80- xff          040  lt  gt              000- 037 x80- xff             x80- xff n 015            x80- xff        040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff      x80- xff n 01 5              x80- xff n 015          040 t              040  lt  gt               000- 037 x80- xff         040  lt  gt              000- 037 x80- xff          x80- xff n 015           x80- xff      x80- xff n 015             lt  gt              x80- xff 000- 010 012- 037               x80- xff n 0 15               x80- xff         x80- xff n 015            x80- xff       x80- xff n 015              x80- xff n 015               x80- xff  n 015           x80- xff      x80- xff n 015            lt  gt               x80- xff 000- 010 012- 037     lt   040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff      x80-  xff n 015              x80- xff n 015          040 t          040 t             x80- xff n 015               x80- xff         x80- xff n 015             x80- xff      x80- xff n 015              x80- xff n 015           040 t           040  lt  gt              000- 037 x80- xff         0 40  lt  gt              000- 037 x80- xff             x80- xff n 015            x80- xff        040 t            x80- xff n 015               x80-  xff         x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040 t            x80 - xff n 015               x80- xff         x80- xff n 015            x 80- xff      x80- xff n 015              x80- xff n 015          040 t            040  lt  gt              000- 037 x80- xff         040  lt  gt               000- 037 x80- xff             x80- xff n 015           x80- xff         040 t            x80- xff n 015               x80- xff         x 80- xff n 015            x80- xff      x80- xff n 015              x80 - xff n 015          040 t            040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff       x80- xff n 015              x80- xff n 015          040 t       040 t             x80- xff n 015               x80- xff         x80- xff n 0 15            x80- xff      x80- xff n 015              x80- xff n 015           040 t           040  lt  gt              000- 037 x80- xff          040  lt  gt              000- 037 x80- xff             x80- xff n 015            x80- xff        040 t            x80- xff n 015               x80 - xff         x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040 t            x 80- xff n 015               x80- xff         x80- xff n 015             x80- xff      x80- xff n 015              x80- xff n 015          040  t           040  lt  gt              000- 037 x80- xff         040  lt  gt               000- 037 x80- xff             x80- xff n 015           x80- xff         040 t            x80- xff n 015               x80- xff          x80- xff n 015            x80- xff      x80- xff n 015              x 80- xff n 015          040 t           040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff       x80- xff n 015              x80- xff n 015          040 t              040  lt  gt              000- 037 x80- xff         040  lt  gt              000-  037 x80- xff         x80- xff n 015           x80- xff      x80- xff  n 015         040 t            x80- xff n 015               x80- xff          x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040 t            x80- xff  n 015               x80- xff         x80- xff n 015            x80- x ff      x80- xff n 015              x80- xff n 015          040 t            040  lt  gt              000- 037 x80- xff         040  lt  gt               000- 037 x80- xff         x80- xff n 015           x80- xff      x80-  xff n 015         040 t            x80- xff n 015               x80- x ff         x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t         040 t            x80- x ff n 015               x80- xff         x80- xff n 015            x80-  xff      x80- xff n 015              x80- xff n 015          040 t            040  lt  gt              000- 037 x80- xff         040  lt  gt               000- 037 x80- xff             x80- xff n 015           x80- xff         040 t            x80- xff n 015               x80- xff         x80-  xff n 015            x80- xff      x80- xff n 015              x80- x ff n 015          040 t           040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff      x80 - xff n 015              x80- xff n 015          040 t           040  lt   gt              000- 037 x80- xff         040  lt  gt              000- 037 x8 0- xff             x80- xff n 015           x80- xff        040 t             x80- xff n 015               x80- xff         x80- xff n 015             x80- xff      x80- xff n 015              x80- xff n 015           040 t       gt   EOF

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The HTML5 spec suggests a simple regex for validating email addresses      a-zA-Z0-9      amp               -    a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9         a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9          This intentionally doesn t comply with RFC 5322      Note  This requirement is a willful violation of RFC 5322  which defines a syntax for e-mail addresses that is simultaneously too strict  before the   character   too vague  after the   character   and too lax  allowing comments  whitespace characters  and quoted strings in manners unfamiliar to most users  to be of practical use here    The total length could also be limited to 254 characters  per RFC 3696  errata 1690

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One simple regular expression which would at least not reject any valid email address would be checking for something  followed by an   sign and then something followed by a period and at least 2 somethings  It won t reject anything  but after reviewing the spec I can t find any email that would be valid and rejected   email                    2

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AS per my understanding most probable will cover by        a-z0-9 -      a-z0-9-       a-z      a-z     a-z      is

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If you need a simple form to validate  you can use the answer of https   regexr com 3e48o    w-        w-        w-  2 4

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I used      A-Za-z0-9-       A-Za-z0-9-      A-Za-z0-9-      A-Za-z0-9-        A-Za-z  2 4       which includes the capitalized letter as well  You wouldn t even need to use tolowercase in this case

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If you are fine with accepting empty values  which is not invalid email  and are running PHP 5 2   I would suggest   static public function checkEmail  email   ignore empty   false            if  ignore empty  amp  amp   is null  email      email                         return true          return filter var  email  FILTER VALIDATE EMAIL

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Maybe the best     a-zA-Z0-9    -    a-zA-Z0-9      a-zA-Z0-9    -   a-zA-Z0-9       a-zA-Z  2 7     Start with a letter or number  may include  quot -    quot   end with  quot   quot  and less than 7 characters  such as  company

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The fully RFC 822 compliant regex is inefficient and obscure because of its length   Fortunately  RFC 822 was superseded twice and the current specification for email addresses is RFC 5322   RFC 5322 leads to a regex that can be understood if studied for a few minutes and is efficient enough for actual use   One RFC 5322 compliant regex can be found at the top of the page at http   emailregex com  but uses the IP address pattern that is floating around the internet with a bug that allows 00 for any of the unsigned byte decimal values in a dot-delimited address  which is illegal   The rest of it appears to be consistent with the RFC 5322 grammar and passes several tests using grep -Po  including cases domain names  IP addresses  bad ones  and account names with and without quotes   Correcting the 00 bug in the IP pattern  we obtain a working and fairly fast regex    Scrape the rendered version  not the markdown  for actual code           a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9             2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9       3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          or       a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9             2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9       3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          Here is diagram of finite state machine for above regexp which is more clear than regexp itself   The more sophisticated patterns in Perl and PCRE  regex library used e g  in PHP  can correctly parse RFC 5322 without a hitch  Python and C  can do that too  but they use a different syntax from those first two  However  if you are forced to use one of the many less powerful pattern-matching languages  then it   s best to use a real parser   It s also important to understand that validating it per the RFC tells you absolutely nothing about whether that address actually exists at the supplied domain  or whether the person entering the address is its true owner  People sign others up to mailing lists this way all the time  Fixing that requires a fancier kind of validation that involves sending that address a message that includes a confirmation token meant to be entered on the same web page as was the address    Confirmation tokens are the only way to know you got the address of the person entering it  This is why most mailing lists now use that mechanism to confirm sign-ups  After all  anybody can put down president whitehouse gov  and that will even parse as legal  but it isn t likely to be the person at the other end   For PHP  you should not use the pattern given in Validate an E-Mail Address with PHP  the Right Way from which I quote      There is some danger that common usage and widespread sloppy coding will establish a de facto standard for e-mail addresses that is more restrictive than the recorded formal standard    That is no better than all the other non-RFC patterns  It isn   t even smart enough to handle even RFC 822  let alone RFC 5322  This one  however  is   If you want to get fancy and pedantic  implement a complete state engine  A regular expression can only act as a rudimentary filter  The problem with regular expressions is that telling someone that their perfectly valid e-mail address is invalid  a false positive  because your regular expression can t handle it is just rude and impolite from the user s perspective  A state engine for the purpose can both validate and even correct e-mail addresses that would otherwise be considered invalid as it disassembles the e-mail address according to each RFC  This allows for a potentially more pleasing experience  like     The specified e-mail address  myemail address com  is invalid  Did you mean  myemail address com     See also Validating Email Addresses  including the comments  Or Comparing E-mail Address Validating Regular Expressions     Debuggex Demo

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List item  I use this function   function checkmail  value            value   trim  value           if  stristr  value                    amp  amp  stristr  value                    amp  amp   strrpos  value       - stripos  value        gt  2                amp  amp   stripos  value        gt  1                amp  amp   strlen  value  - strrpos  value        lt  6                amp  amp   strlen  value  - strrpos  value        gt  2                amp  amp    value    preg replace               value                 amp  amp    value    preg replace     A-Za-z0-9 -               value                        else              return  Invalid Mail-Id

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It all depends on how accurate you want to be   For my purposes  where I m just trying to keep out things like bob   aol com  spaces in emails  or steve  no domain at all  or mary aolcom  no period before  com   I use     S   S    S      Sure  it will match things that aren t valid email addresses  but it s a matter of getting common simple errors   There are any number of changes that can be made to that regex  and some are in the comments for this answer   but it s simple  and easy to understand  and is a fine first attempt

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The regular expression for an email address is      quot       -    - u 10FFFF       t - u 10FFFF     quot     -    - -9  A-Z  - u 10FFFF           -    - -9  A-Z  - u 10FFFF          -    - -9  A-Z  - u 10FFFF           -    - -9  A-Z  - u 10FFFF         -Z  - u 10FFFF        u  This regular expression is 100  identical to the addr-spec ABNF for non-obsolete email addresses  as specified across RFC 5321  RFC 5322  and RFC 6532  Additionally  you must verify   The email address is well-formed UTF-8  or ASCII  if you cannot send to internationalized email addresses  The address is not more than 320 UTF-8 bytes The user part  the first match group  is not more than 64 UTF-8 bytes The domain part  the second match group  is not more than 255 UTF-8 bytes  The easiest way to do all of this is to use an existing function  In PHP  see the filter var function using FILTER VALIDATE EMAIL and FILTER FLAG EMAIL UNICODE  if you can send to internationalized email addresses    email valid   filter var  email input  FILTER VALIDATE EMAIL  FILTER FLAG EMAIL UNICODE    However  maybe you re building such a function   indeed the easiest way to implement this is to use a regular expression  Remember  this only verifies that the email address will not cause a syntax error  The only way to verify that the address can receive email is to actually send an email  Next  I will treat how you generate this regular expression   I write a new answer  because most of the answers here make the mistake of either specifying a pattern that is too restrictive  and so have not aged well   or they present a regular expression that s actually matching a header for a MIME message  and not the email address itself  It is entirely possible to make a regular expression from an ABNF  so long as there are no recursive parts  RFC 5322 specifies what is legal to send in a MIME message  consider this the upper bound on what is a legal email address  However  to follow this ABNF exactly would be a mistake  this pattern technically represents how you encode an email address in a MIME message  and allows strings not part of the email address  like folding whitespace and comments  and it includes support for obsolete forms that are not legal to generate  but that servers read for historical reasons    An email address does not include these  RFC 5322 explains   Both atom and dot-atom are interpreted as a single unit  comprising the string of characters that make it up   Semantically  the optional comments and FWS surrounding the rest of the characters are not part of the atom  the atom is only the run of atext characters in an atom  or the atext and  quot   quot  characters in a dot-atom    In some of the definitions  there will be non-terminals whose names start with  quot obs- quot    These  quot obs- quot  elements refer to tokens defined in the obsolete syntax in section 4   In all cases  these productions are to be ignored for the purposes of generating legal Internet messages and MUST NOT be used as part of such a message   If you remove CFWS  BWS  and obs-  rules from the addr-spec in RFC 5322  and perform some optimization on the result  I used  quot greenery quot    you can produce this regular expression  quoted with slashes and anchored  suitable for use in ECMAScript and compatible dialects  with added newline for clarity       quot       -    -       t -     quot     -    - -9  A-Z  -           -    - -9  A-Z  -           -    - -9  A-Z  -           -    - -9  A-Z  -         -Z  -          This only supports ASCII email addresses  To support RFC 6532 Internationalized Email Addresses  replace the   character with  u 10FFFF   PHP  ECMAScript with the u flag   or  uFFFF  for UTF-16 implementations  like  Net and older ECMAScript JavaScript       quot       -    - u 10FFFF       t - u 10FFFF     quot     -    - -9  A-Z  - u 10FFFF           -    - -9  A-Z  - u 10FFFF          -    - -9  A-Z  - u 10FFFF           -    - -9  A-Z  - u 10FFFF         -Z  - u 10FFFF        u  This works because the ABNF we are using is not recursive  and so forms a non-recursive  regular grammar that can be converted into a regular expression  It breaks down like so   The user part  before the    may be a dot-atom or a quoted-string  quot     -    -       t -     quot  specifies the quoted-string form of the user  e g   quot root home quot  example com  It permits any non-control character inside double quotes  except that spaces  tabs  doublequotes  and backslashes must be backslash-escaped     -    - -9  A-Z  -   is the first character of the dot-atom of the user         -    - -9  A-Z  -     matches the rest of the dot-atom  allowing dots  except after another dot  or as the final character     denotes the domain  The domain part may be a dot-atom or a domain-literal     -    - -9  A-Z  -         -    - -9  A-Z  -     is the same dot-atom form as above  but here it represents domain names and IPv4 addresses      -Z  -      will match IPv6 addresses and future definitions of host names   This RegExp allows all spec-compliant email addresses  and can be used verbatim in a MIME message  except for line length limits  in which case folding whitespace must be added   This also sets non-capturing groups such that match 1  will be the user  match 2  will be the host   However if match 1  starts with a double quote  then filter out backslash escapes  and the start and end double quotes   quot root quot  example com and root example com identify the same inbox   Finally  note that RFC 5321 sets limits on how long an email address may be  The user part may be up to 64 bytes  and the domain part may be up to 255 bytes  Including the   character  the limit for the entire address is 320 bytes  This is measured in bytes after the address is UTF-8 encoded  not characters  Note that RFC 5322 ABNF defines a permissive syntax for domain names  allowing names currently known to be invalid  This also allows for domain names that could become legal in the future  This should not be a problem  as this should be handled the same way a non-existent domain name is  Always consider the possibility that a user typed in an email address that works  but that they do not have access to  The only foolproof way to verify an email address is to send an email  This is adapted from my article E-Mail Addresses  amp  Syntax

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I found a regular expression that is compliant to RFC 2822  The preceding standard to  RFC 5322  This regular expression appears to perform fairly well and will cover most cases  however with RFC 5322 becoming the standard there may be some holes that ought to be plugged        a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9            25 0-5  2 0-4  0-9   01   0-9  0-9       3    25 0-5  2 0-4  0-9   01   0-9  0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f           The documentation says you shouldn t use the above regular expression  but instead favour this flavour  which is a bit more manageable    a-z0-9     amp              -        a-z0-9     amp              -         a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9      I noticed this is case-sensitive  so I actually made an alteration to this landing     a-zA-Z0-9     amp              -        a-zA-Z0-9     amp              -         a-zA-Z0-9     a-zA-Z0-9-   a-zA-Z0-9        a-zA-Z0-9     a-zA-Z0-9-   a-zA-Z0-9

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Writing a regular expression for all the things will take a lot of effort  Instead  you can use pyIsEmail package   Below text is taken from pyIsEmail website   pyIsEmail is a no-nonsense approach for checking whether that user-supplied email address could be real   Regular expressions are cheap to write  but often require maintenance when new top-level domains come out or don   t conform to email addressing features that come back into vogue  pyIsEmail allows you to validate an email address     and even check the domain  if you wish     with one simple call  making your code more readable and faster to write  When you want to know why an email address doesn   t validate  they even provide you with a diagnosis   Usage  For the simplest usage  import and use the is email function   from pyisemail import is email  address    test example com  bool result   is email address  detailed result   is email address  diagnose True    You can also check whether the domain used in the email is a valid domain and whether or not it has a valid MX record   from pyisemail import is email  address    test example com  bool result with dns   is email address  check dns True  detailed result with dns   is email address  check dns True  diagnose True    These are primary indicators of whether an email address can even be issued at that domain  However  a valid response here is not a guarantee that the email exists  merely that is can exist   In addition to the base is email functionality  you can also use the validators by themselves  Check the validator source doc to see how this works

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Don t know about best  but this one is at least correct  as long as the addresses have their comments stripped and replaced with whitespace   Seriously  You should use an already written library for validating emails  The best way is probably to just send a verification e-mail to that address

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We have used http   www aspnetmx com  with a degree of success for a few years now  You can choose the level you want to validate at  e g  syntax check  check for the domain  mx records or the actual email    For front-end forms we generally verify that the domain exists and the syntax is correct  then we do stricter verification to clean out our database before doing bulk mail-outs

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For Angular2   Angular7 I use this pattern    x000D   x000D  emailPattern      a-zA-Z0-9   -    a-zA-Z0-9-       a-zA-Z0-9-      s     x000D   x000D  private createForm     x000D    this form   this formBuilder group   x000D      email        Validators required  Validators pattern this emailPattern    x000D        x000D    x000D   x000D   x000D    It also allows for extra spaces at the end  which you should truncate before sending it to the backend  but some users  especially on mobile are easy to mistakenly add a space at the end

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Don t know about best  but this one is at least correct  as long as the addresses have their comments stripped and replaced with whitespace   Seriously  You should use an already written library for validating emails  The best way is probably to just send a verification e-mail to that address

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Just about every RegEx I ve seen - including some used by Microsoft will not allow the following valid email to get through   simon- hotmail com  Just had a real customer with an email address in this format who couldn t place an order   Here s what I settled on     A minimal Regex that won t have false negatives  Alternatively use the MailAddress constructor with some additional checks  see below   Checking for common typos  cmo or  gmial com and asking for confirmation Are you sure this is your correct email address  It looks like there may be a mistake  Allow the user to accept what they typed if they are sure  Handling bounces when the email is actually sent and manually verifying them to check for obvious mistakes              try                       var email   new MailAddress str                if  email Host EndsWith   cmo                                  return EmailValidation PossibleTypo                             if   email Host EndsWith       amp  amp  email Host Contains                                     return EmailValidation OK                                  catch                       return EmailValidation Invalid

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The email addresses I want to validate are going to be used by an ASP NET web application using the System Net Mail namespace to send emails to a list of people   So  rather than using some very complex regular expression  I just try to create a MailAddress instance from the address  The MailAddress constructor will throw an exception if the address is not formed properly  This way  I know I can at least get the email out of the door  Of course this is server-side validation  but at a minimum you need that anyway   protected void emailValidator ServerValidate object source  ServerValidateEventArgs args        try               var a   new MailAddress txtEmail Text             catch  Exception ex                args IsValid   false          emailValidator ErrorMessage    email      ex Message

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You can use following regular Expression for any email address        lt  gt             s           lt  gt             s                        0-9  1 3    0-9  1 3    0-9  1 3    0-9  1 3        a-zA-Z -0-9       a-zA-Z  2        For PHP    function checkEmailValidation  email                       expression         lt  gt             s           lt  gt             s                        0-9  1 3    0-9  1 3    0-9  1 3    0-9  1 3        a-zA-Z -0-9       a-zA-Z  2                 if preg match  expression   email                         return true           else                       return false                   For Javascript   function checkEmailValidation email                       var pattern         lt  gt             s           lt  gt             s                        0-9  1 3    0-9  1 3    0-9  1 3    0-9  1 3        a-zA-Z -0-9       a-zA-Z  2                 if pattern test email                         return true           else                       return false

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The email addresses I want to validate are going to be used by an ASP NET web application using the System Net Mail namespace to send emails to a list of people   So  rather than using some very complex regular expression  I just try to create a MailAddress instance from the address  The MailAddress constructor will throw an exception if the address is not formed properly  This way  I know I can at least get the email out of the door  Of course this is server-side validation  but at a minimum you need that anyway   protected void emailValidator ServerValidate object source  ServerValidateEventArgs args        try               var a   new MailAddress txtEmail Text             catch  Exception ex                args IsValid   false          emailValidator ErrorMessage    email      ex Message

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For Angular2   Angular7 I use this pattern    x000D   x000D  emailPattern      a-zA-Z0-9   -    a-zA-Z0-9-       a-zA-Z0-9-      s     x000D   x000D  private createForm     x000D    this form   this formBuilder group   x000D      email        Validators required  Validators pattern this emailPattern    x000D        x000D    x000D   x000D   x000D    It also allows for extra spaces at the end  which you should truncate before sending it to the backend  but some users  especially on mobile are easy to mistakenly add a space at the end

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Valid RegEx according to w3 org and wikipedia   A-Z0-9a-z      amp    -              A-Za-z0-9 -      A-Za-z  2 4    e g       amp    -            example com

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I use multi-step validation  As there is no perfect way to validate email address  perfect one can t be made  but at least you can notify user he she is doing something wrong - here is my approach  1  I first validate with the very basic regex which just checks if email contains exactly one   sign and it is not blank before or after that sign  e g        s       s      2a  if the first validator does not pass  and for most addresses it should although it is not perfect   then warn the user the email is invalid and do not allow him her to continue with the input  2b  if it passes  then validate against more strict regex - something which might disallow valid emails  If it does not pass  user is warned about possible error but allowed to continue  Unlike the step  1  where the user is not allowed to continue because it is an obvious error   So in other words  the first liberal validation is just to strip obvious errors and it is treated as  error   People type a blank address  address without   sign and so on  This should be treated as error  The second one is more strict but treated as  warning  and user is allowed to continue with the input but warned to at least examine if he she entered a valid entry  The key here is in error warning approach - error being something which can t under 99 99  circumstances be valid email   Of couse  you can adjust what makes a first regex more liberal and second one more strict   Depending on what you need  the above approach might work for you

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We have used http   www aspnetmx com  with a degree of success for a few years now  You can choose the level you want to validate at  e g  syntax check  check for the domain  mx records or the actual email    For front-end forms we generally verify that the domain exists and the syntax is correct  then we do stricter verification to clean out our database before doing bulk mail-outs

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You could use the one employed by the jQuery Validation plugin         a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF        a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x22      x20  x09    x0d x0a     x20  x09        x01- x08 x0b x0c x0e- x1f x7f   x21   x23- x5b    x5d- x7e    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF         x01- x09 x0b x0c x0d- x7f    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x20  x09    x0d x0a     x20  x09      x22        a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF           a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF         i

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Java Mail API does magic for us      try            InternetAddress internetAddress   new InternetAddress email        internetAddress validate         return true            catch Exception ex                return false          I got this from here

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I would not suggest to use an regex at all - email addresses are way too complicated for that  This is a common problem so I would guess there are many libraries that contain a validator - if you use Java the EmailValidator of apache commons validator is a good one

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This rule matches what our postfix server could not send to   allow letters  numbers  -            amp         no -foo bar com  no asd -bar com      a-z0-9        amp    -a-z0-9        amp         a-z0-9  -a-z0-9       -a-z0-9       a-z  2     i

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RFC 5322 standard   Allows dot-atom local-part  quoted-string local-part  obsolete  mixed dot-atom and quoted-string  local-part  domain name domain   IPv4  IPv6  and IPv4-mapped IPv6 address  domain literal domain  and  nested  CFWS            gt   1      gt      -            1   255         gt   1      gt      -            1   65        gt    gt    gt     gt    gt    gt  x0D x0A    t        gt   t    x0D x0A    t            gt   2    gt   x01- x08 x0B x0C x0E-   -    - x7F       x00- x7F    3      2        2     2        -      -9   - -       gt   2    gt   x01- x08 x0B x0C x0E-  -    - x7F       x00- x7F      2      gt   1     1   4     1       1  a-z0-9-  64     1    gt   a-z0-9    gt  a-z0-9-   a-z0-9       gt   1        1  a-z0-9-  64     1   5   0 126          gt IPv6    gt   a-f0-9  1 4     gt    6   7           a-f0-9        8      6    gt    6   0 6       7        gt    gt IPv6    gt   6    gt    6   5            a-f0-9    6     8       gt    6    gt    6   0 4         25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9     gt     9   3        1   isD    RFC 5321 standard   Allows dot-atom local-part  quoted-string local-part  domain name domain  and  IPv4  IPv6  and IPv4-mapped IPv6 address  domain literal domain            gt      gt      -            255           gt      -         65         gt     -      -9   - -      gt     1        gt     -    -        -                 64      gt   a-z0-9    gt  a-z0-9-   a-z0-9       gt     2   0 126          gt IPv6    gt   a-f0-9  1 4     gt    3   7           a-f0-9        8      3    gt    3   0 6       4        gt    gt IPv6    gt   3    gt    3   5            a-f0-9    6     5       gt    3    gt    3   0 4         25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9     gt     6   3        iD    Basic   Allows dot-atom local-part and domain name domain  requiring at least two domain name labels with the TLD limited to 2-6 alphabetic characters            255        65        -     -9   - -      gt     1              64      gt  a-z0-9    gt  a-z0-9-   a-z0-9       1 126  a-z  2 6   iD

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I found nice article  which says that the best way to validate e-mail address is that regex expresion              i

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For PHP I m using email address validator from Nette Framework - http   api nette org 2 3 3 source-Utils Validators php html 234-247     public static    function isEmail  value         atom     -a-z0-9     amp                     RFC 5322 unquoted characters in local-part      localPart                 x23-  x5B  x5D-  x7E         -        atom        atom          quoted or unquoted      alpha    a-z x80- xFF      superset of IDN      domain     0-9 alpha     -0-9 alpha  0 61  0-9 alpha         RFC 1034 one domain component      topDomain      alpha     -0-9 alpha  0 17   alpha          return  bool  preg match     localPart     domain      topDomain  z i    value

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I don t believe the claim made by bortzmeyer  above  that  The grammar  specified in RFC 5322  is too complicated for that   to be handled by a regular expression    Here is the grammar   from http   tools ietf org html rfc5322 section-3 4 1   addr-spec           local-part     domain local-part          dot-atom   quoted-string   obs-local-part domain              dot-atom   domain-literal   obs-domain domain-literal       CFWS         FWS  dtext   FWS       CFWS  dtext                d33-90              Printable US-ASCII                      d94-126              characters not including                     obs-dtext                       or       Assuming that dot-atom  quoted-string  obs-local-part  obs-domain are themselves regular languages  this is a very simple grammar  Just replace the local-part and domain in the addr-spec production with their respective productions  and you have a regular language  directly translatable to a regular expression

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According to official standard RFC 2822 valid email regex is       a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9            25 0-5  2 0-4  0-9   01   0-9  0-9       3    25 0-5  2 0-4  0-9   01   0-9  0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          if you want to use it in Java its really very easy  import java util regex     class regexSample       public static void main String args                  Input the string for validation       String email    xyz hotmail com            Set the email pattern string       Pattern p   Pattern compile       a-z0-9     amp              -         a-z0-9     amp              -                             x01-  x08  x0b  x0c  x0e-  x1f  x21  x23-  x5b  x5d-  x7f       x01-  x09  x0b  x0c  x0e-  x7f                                        a-z0-9     a-z0-9-   a-z0-9         a-z0-9     a-z0-9-   a-z0-9             25 0-5  2 0-4  0-9   01   0-9  0-9        3    25 0-5  2 0-4  0-9   01   0-9  0-9    a-z0-9-   a-z0-9        x01-  x08  x0b  x0c  x0e-  x1f  x21-  x5a  x53-  x7f       x01-  x09  x0b  x0c  x0e-  x7f                    Match the given string with the pattern       Matcher m   p matcher email            check whether match is found        boolean matchFound   m matches           if  matchFound          System out println  Valid Email Id           else         System out println  Invalid Email Id

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I never bother creating with my own regular expression  because chances are that someone else has already come up with a better version   I always use regexlib to find one to my liking

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The HTML5 spec suggests a simple regex for validating email addresses      a-zA-Z0-9      amp               -    a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9         a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9          This intentionally doesn t comply with RFC 5322      Note  This requirement is a willful violation of RFC 5322  which defines a syntax for e-mail addresses that is simultaneously too strict  before the   character   too vague  after the   character   and too lax  allowing comments  whitespace characters  and quoted strings in manners unfamiliar to most users  to be of practical use here    The total length could also be limited to 254 characters  per RFC 3696  errata 1690

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This regex is from Perl s Email  Valid library  I believe it to be the most accurate  it matches all 822  And  it is based on the regular expression in the O Reilly book      Regular expression built using Jeffrey Friedl s example in   Mastering Regular Expressions  http   www ora com catalog regexp       RFC822PAT    lt  lt  EOF     040 t            x80- xff n 015               x80- xff         x80-  xff n 015            x80- xff      x80- xff n 015              x80- xf f n 015          040 t              040  lt  gt              000- 037 x80- x ff         040  lt  gt              000- 037 x80- xff         x80- xff n 015            x80- xff      x80- xff n 015         040 t            x80-  xff n 015               x80- xff         x80- xff n 015            x80 - xff      x80- xff n 015              x80- xff n 015          040 t            040 t            x80- xff n 015               x80- xff          x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040  lt  gt              000- 037 x8 0- xff         040  lt  gt              000- 037 x80- xff         x80- xff n  015           x80- xff      x80- xff n 015         040 t            x 80- xff n 015               x80- xff         x80- xff n 015             x80- xff      x80- xff n 015              x80- xff n 015          040  t         040 t            x80- xff n 015               x80- xff          x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040  lt  gt              000- 037  x80- xff         040  lt  gt              000- 037 x80- xff             x80-  xff n 015           x80- xff        040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff       x80- xff n 015              x80- xff n 015          040 t           04 0 t            x80- xff n 015               x80- xff         x80- xff  n 015            x80- xff      x80- xff n 015              x80- xff n  015          040 t           040  lt  gt              000- 037 x80- xff          040  lt  gt              000- 037 x80- xff             x80- xff n 015            x80- xff        040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff      x80- xff n 01 5              x80- xff n 015          040 t              040  lt  gt               000- 037 x80- xff         040  lt  gt              000- 037 x80- xff          x80- xff n 015           x80- xff      x80- xff n 015             lt  gt              x80- xff 000- 010 012- 037               x80- xff n 0 15               x80- xff         x80- xff n 015            x80- xff       x80- xff n 015              x80- xff n 015               x80- xff  n 015           x80- xff      x80- xff n 015            lt  gt               x80- xff 000- 010 012- 037     lt   040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff      x80-  xff n 015              x80- xff n 015          040 t          040 t             x80- xff n 015               x80- xff         x80- xff n 015             x80- xff      x80- xff n 015              x80- xff n 015           040 t           040  lt  gt              000- 037 x80- xff         0 40  lt  gt              000- 037 x80- xff             x80- xff n 015            x80- xff        040 t            x80- xff n 015               x80-  xff         x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040 t            x80 - xff n 015               x80- xff         x80- xff n 015            x 80- xff      x80- xff n 015              x80- xff n 015          040 t            040  lt  gt              000- 037 x80- xff         040  lt  gt               000- 037 x80- xff             x80- xff n 015           x80- xff         040 t            x80- xff n 015               x80- xff         x 80- xff n 015            x80- xff      x80- xff n 015              x80 - xff n 015          040 t            040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff       x80- xff n 015              x80- xff n 015          040 t       040 t             x80- xff n 015               x80- xff         x80- xff n 0 15            x80- xff      x80- xff n 015              x80- xff n 015           040 t           040  lt  gt              000- 037 x80- xff          040  lt  gt              000- 037 x80- xff             x80- xff n 015            x80- xff        040 t            x80- xff n 015               x80 - xff         x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040 t            x 80- xff n 015               x80- xff         x80- xff n 015             x80- xff      x80- xff n 015              x80- xff n 015          040  t           040  lt  gt              000- 037 x80- xff         040  lt  gt               000- 037 x80- xff             x80- xff n 015           x80- xff         040 t            x80- xff n 015               x80- xff          x80- xff n 015            x80- xff      x80- xff n 015              x 80- xff n 015          040 t           040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff       x80- xff n 015              x80- xff n 015          040 t              040  lt  gt              000- 037 x80- xff         040  lt  gt              000-  037 x80- xff         x80- xff n 015           x80- xff      x80- xff  n 015         040 t            x80- xff n 015               x80- xff          x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t           040 t            x80- xff  n 015               x80- xff         x80- xff n 015            x80- x ff      x80- xff n 015              x80- xff n 015          040 t            040  lt  gt              000- 037 x80- xff         040  lt  gt               000- 037 x80- xff         x80- xff n 015           x80- xff      x80-  xff n 015         040 t            x80- xff n 015               x80- x ff         x80- xff n 015            x80- xff      x80- xff n 015               x80- xff n 015          040 t         040 t            x80- x ff n 015               x80- xff         x80- xff n 015            x80-  xff      x80- xff n 015              x80- xff n 015          040 t            040  lt  gt              000- 037 x80- xff         040  lt  gt               000- 037 x80- xff             x80- xff n 015           x80- xff         040 t            x80- xff n 015               x80- xff         x80-  xff n 015            x80- xff      x80- xff n 015              x80- x ff n 015          040 t           040 t            x80- xff n 015                x80- xff         x80- xff n 015            x80- xff      x80 - xff n 015              x80- xff n 015          040 t           040  lt   gt              000- 037 x80- xff         040  lt  gt              000- 037 x8 0- xff             x80- xff n 015           x80- xff        040 t             x80- xff n 015               x80- xff         x80- xff n 015             x80- xff      x80- xff n 015              x80- xff n 015           040 t       gt   EOF

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Cal Henderson  Flickr  wrote an article called Parsing Email Adresses in PHP and shows how to do proper RFC  2 822-compliant Email Address parsing   You can also get the source code in php  python and ruby which is cc licensed

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There is not one which is really usable  I discuss some issues in my answer to Is there a php library for email address validation   it is discussed also in Regexp recognition of email address hard   In short  don t expect a single  usable regex to do a proper job  And the best regex will validate the syntax  not the validity of an e-mail  jhohn example com is correct but it will probably bounce

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While deciding which characters are allowed  please remember your apostrophed and hyphenated friends  I have no control over the fact that my company generates my email address using my name from the HR system  That includes the apostrophe in my last name  I can t tell you how many times I have been blocked from interacting with a website by the fact that my email address is  invalid

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RFC 5322 standard   Allows dot-atom local-part  quoted-string local-part  obsolete  mixed dot-atom and quoted-string  local-part  domain name domain   IPv4  IPv6  and IPv4-mapped IPv6 address  domain literal domain  and  nested  CFWS            gt   1      gt      -            1   255         gt   1      gt      -            1   65        gt    gt    gt     gt    gt    gt  x0D x0A    t        gt   t    x0D x0A    t            gt   2    gt   x01- x08 x0B x0C x0E-   -    - x7F       x00- x7F    3      2        2     2        -      -9   - -       gt   2    gt   x01- x08 x0B x0C x0E-  -    - x7F       x00- x7F      2      gt   1     1   4     1       1  a-z0-9-  64     1    gt   a-z0-9    gt  a-z0-9-   a-z0-9       gt   1        1  a-z0-9-  64     1   5   0 126          gt IPv6    gt   a-f0-9  1 4     gt    6   7           a-f0-9        8      6    gt    6   0 6       7        gt    gt IPv6    gt   6    gt    6   5            a-f0-9    6     8       gt    6    gt    6   0 4         25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9     gt     9   3        1   isD    RFC 5321 standard   Allows dot-atom local-part  quoted-string local-part  domain name domain  and  IPv4  IPv6  and IPv4-mapped IPv6 address  domain literal domain            gt      gt      -            255           gt      -         65         gt     -      -9   - -      gt     1        gt     -    -        -                 64      gt   a-z0-9    gt  a-z0-9-   a-z0-9       gt     2   0 126          gt IPv6    gt   a-f0-9  1 4     gt    3   7           a-f0-9        8      3    gt    3   0 6       4        gt    gt IPv6    gt   3    gt    3   5            a-f0-9    6     5       gt    3    gt    3   0 4         25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9     gt     6   3        iD    Basic   Allows dot-atom local-part and domain name domain  requiring at least two domain name labels with the TLD limited to 2-6 alphabetic characters            255        65        -     -9   - -      gt     1              64      gt  a-z0-9    gt  a-z0-9-   a-z0-9       1 126  a-z  2 6   iD

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hmm strange not to see this answer already within the answers  Here is the one I ve build  It is not a bulletproof version but it is  simple  and checks almost everything     w -         w -       w -         w -          a-zA-Z  2 4     I think an explanation is in place so you can modify it if you want    e     w -   matches a-z  A-Z        - at least one time    m          w -     matches a-z  A-Z        - zero or more times but need to start with a    dot            i     w -   matches a-z  A-Z        - at least one time    l          w -     matches a-z  A-Z        - zero or more times but need to start with a    dot     com         a-zA-Z  2 4   matches a-z  A-Z for 2 to 4 times starting with a    dot   giving e  m  i  l  com where   m  and   l  are optional but also can be repeated multiple times  I think this validates all valid email addresses but blocks potential invalid without using an over complex regular expression which won t be necessary in most cases   notice this will allow   - com but that is the compromise for keeping it simple

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this simple pattern works for me      lt name gt    lt  gt         s   quot   1       lt domain gt    lt  gt         s   quot   2       lt top gt    lt  gt          s   quot   2

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There are plenty examples of this out on the net  and I think even one that fully validates the RFC - but it s tens hundreds of lines long if memory serves   People tend to get carried away validating this sort of thing  Why not just check it has an   and at least one   and meets some simple minimum length  It s trivial to enter a fake email and still match any valid regex anyway  I would guess that false positives are better than false negatives

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World s most popular blogging platform WordPress uses this function to validate email address    But they are doing it with multiple steps     You don t have to worry anymore when using the regex mentioned in this function     Here is the function            Verifies that an email is valid        Does not grok i18n domains  Not RFC compliant         since 0 71        param string  email Email address to verify      param boolean  deprecated Deprecated      return string bool Either false or the valid email address      function is email   email   deprecated   false         if     empty   deprecated              deprecated argument    FUNCTION     3 0             Test for the minimum length the email can be     if   strlen   email    lt  3             return apply filters   is email   false   email   email too short                   Test for an   character after the first position     if   strpos   email       1       false             return apply filters   is email   false   email   email no at                   Split out the local and domain parts     list   local   domain     explode        email  2            LOCAL PART        Test for invalid characters     if    preg match      a-zA-Z0-9     amp                  -        local               return apply filters   is email   false   email   local invalid chars                   DOMAIN PART        Test for sequences of periods     if   preg match       2       domain               return apply filters   is email   false   email   domain period sequence                   Test for leading and trailing periods and whitespace     if   trim   domain     t n r 0 x0B          domain             return apply filters   is email   false   email   domain period limits                   Split the domain into subs      subs   explode        domain            Assume the domain will have at least two subs     if   2  gt  count   subs               return apply filters   is email   false   email   domain no periods                   Loop through each sub     foreach    subs as  sub                Test for leading and trailing hyphens and whitespace         if   trim   sub     t n r 0 x0B-         sub                 return apply filters   is email   false   email   sub hyphen limits                           Test for invalid characters         if    preg match     a-z0-9-    i    sub                   return apply filters   is email   false   email   sub invalid chars                             Congratulations your email made it      return apply filters   is email    email   email  null

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For a vivid demonstration  the following monster is pretty good but still does not correctly recognize all syntactically valid email addresses  it recognizes nested comments up to four levels deep   This is a job for a parser  but even if an address is syntactically valid  it still may not be deliverable  Sometimes you have to resort to the hillbilly method of  Hey  y all  watch ee-us       derivative of work with the following copyright and license     Copyright  c  2004 Casey West   All rights reserved     This module is free software  you can redistribute it and or    modify it under the same terms as Perl itself      see http   search cpan org  cwest Email-Address-1 80   private static string gibberish        -xism      -xism   -xism   -xism   -xism   -xism   -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s    s      s      x00- x1F x7F   lt  gt            lt DQ gt  s    -xism   -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s    s      s       -xism   -xism   -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D      -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A x 0D         s    s       s    s     s    lt DQ gt   -xism   -xism       lt DQ gt      -xism     -xism    x0A x0D      lt DQ gt   -xism   -xi sm  s       s   -xism   -xism    gt              -xism     -xis m    x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s     s     s          -xism   -xism   -xism  s       s   -xism    -xism    gt              -xism     -xism    x0A x0D      -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D         s    s       s    s     s    lt   -xism   -xi sm   -xism   -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s    -xism   -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s     -xism    x00- x1F x7F   lt   gt            lt DQ gt  s          x00- x1F x7F   lt  gt            lt DQ gt  s        -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s   -xism    -xism    gt              -xism     -xism    x0A x0D         s     s       s    s     s       -xism   -xism   -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A x 0D      -xism  s       s   -xism   -xism    gt              -xi sm     -xism    x0A x0D         s    s       s    s     s     lt DQ gt   -xism   -xism      lt DQ gt      -xism     -xism    x0A x0D       lt DQ gt   -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s   -x ism   -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s         -xism   -xism   -xism    -xism  s       s   -xism   -xism    gt              -xism      -xism    x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s     s     s     -xism    x00- x1F x7F   lt  gt            lt DQ gt  s           x00- x1F x7F   lt  gt            lt DQ gt  s       -xism   -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s    s      s       -xism   -xism   -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D      -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A  x0D         s    s       s    s     s         s   -xism   -x ism              -xism     -xism    x0A x0D        s     -xi sm   -xism  s       s   -xism   -xism    gt              -xism      -xism    x0A x0D      -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D         s    s        s    s     s       gt   -xism   -xism  s       s   -xism   - xism    gt              -xism     -xism    x0A x0D      -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D         s    s       s    s     s        -xism   -x ism   -xism   -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s    -xism   -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s     -xism    x00- x1F x7F    lt  gt            lt DQ gt  s          x00- x1F x7F   lt  gt            lt DQ gt  s        -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s   -xism    -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s       -xism   -xism   -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A  x0D      -xism  s       s   -xism   -xism    gt              -x ism     -xism    x0A x0D         s    s       s    s     s     lt DQ gt   -xism   -xism      lt DQ gt      -xism     -xism    x0A x0D       lt DQ gt   -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s   - xism   -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s         -xism   -xism   -xism    -xism  s       s   -xism   -xism    gt              -xism      -xism    x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s        s    s     s     -xism    x00- x1F x7F   lt  gt            lt DQ gt  s           x00- x1F x7F   lt  gt            lt DQ gt  s       -xism   -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s    s      s       -xism   -xism   -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D      -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A  x0D         s    s       s    s     s         s   -xism   - xism              -xism     -xism    x0A x0D        s     -x ism   -xism  s       s   -xism   -xism    gt              -xism      -xism    x0A x0D      -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D         s    s        s    s     s         -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D      -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A x0 D         s    s       s    s         Replace   lt DQ gt             Replace   t          Replace             Replace   r          Replace   n         private static Regex mailbox     new Regex gibberish  RegexOptions ExplicitCapture

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Nice  I converted the code into java to match the compiler  String pattern       a-zA-Z0-9     amp              -         a-zA-Z0-9     amp              -             x01-  x08  x0b  x0c  x0e-  x1f  x21  x23-  x5b  x5d-  x7f         x01-  x09  x0b  x0c  x0e-  x7f              a-zA-Z0-9     a-zA-Z0-9-   a-zA-Z0-9         a-zA-Z0-9     a-zA-Z0-9-   a-zA-Z0-9              2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9        3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-zA-Z0-9-   a-zA-Z0-9        x01-  x08  x0b  x0c  x0e-  x1f  x21-  x5a  x53-  x7f         x01-  x09  x0b  x0c  x0e-  x7f

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According to RFC 2821 and RFC 2822  the local-part of an email addresses may use any of these ASCII characters     Uppercase and lowercare letters The digits 0 through 9  The characters       amp    -            The character     provided that it is not the first or last character in the local-part    Matches     a amp d somedomain com a d somedomain com a d somedomain com   Non-Matches     abc somedomain com abc  somedomain com a b somedomain com   For one that is RFC 2821  2822 Compliant you can use             amp     -           w          amp     -           w       amp     -             w  0        amp     -           w       w   -   w      w   -   w        Email - RFC 2821  2822 Compliant

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Quick answer  Use the following regex for input validation     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -         0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       Addresses matched by this regex    have a local part  i e  the part before the  -sign  that is strictly compliant with RFC 5321 5322  have a domain part  i e  the part after the  -sign  that is a host name with at least two labels  each of which is at most 63 characters long    The second constraint is a restriction on RFC 5321 5322   Elaborate answer  Using a regular expression that recognizes email addresses could be useful in various situations  for example to scan for email addresses in a document  to validate user input  or as an integrity constraint on a data repository   It should however be noted that if you want to find out if the address actually refers to an existing mailbox  there s no substitute for sending a message to the address  If you only want to check if an address is grammatically correct then you could use a regular expression  but note that       is a grammatically correct email address that certainly doesn t refer to an existing mailbox   The syntax of email addresses has been defined in various RFCs  most notably RFC 822 and RFC 5322  RFC 822 should be seen as the  original  standard and RFC 5322 as the latest standard  The syntax defined in RFC 822 is the most lenient and subsequent standards have restricted the syntax further and further  where newer systems or services should recognize obsolete syntax  but never produce it   In this answer I   ll take    email address    to mean addr-spec as defined in the RFCs  i e  jdoe example org  but not  John Doe  lt jdoe example org gt   nor some-group jdoe example org mrx exampel org     There s one problem with translating the RFC syntaxes into regexes  the syntaxes are not regular  This is because they allow for optional comments in email addresses that can be infinitely nested  while infinite nesting can t be described by a regular expression  To scan for or validate addresses containing comments you need a parser or more powerful expressions   Note that languages like Perl have constructs to describe context free grammars in a regex-like way   In this answer I ll disregard comments and only consider proper regular expressions   The RFCs define syntaxes for email messages  not for email addresses as such  Addresses may appear in various header fields and this is where they are primarily defined  When they appear in header fields addresses may contain  between lexical tokens  whitespace  comments and even linebreaks  Semantically this has no significance however  By removing this whitespace  etc  from an address you get a semantically equivalent canonical representation  Thus  the canonical representation of first  last  comment       3 5 7 9  is first last  3 5 7 9    Different syntaxes should be used for different purposes  If you want to scan for email addresses in a  possibly very old  document it may be a good idea to use the syntax as defined in RFC 822  On the other hand  if you want to validate user input you may want to use the syntax as defined in RFC 5322  probably only accepting canonical representations  You should decide which syntax applies to your specific case   I use POSIX  extended  regular expressions in this answer  assuming an ASCII compatible character set   RFC 822  I arrived at the following regular expression  I invite everyone to try and break it  If you find any false positives or false negatives  please post them in a comment and I ll try to fix the expression as soon as possible           lt  gt           x00- x1F x7F      n     r         r n       r        r               lt  gt           x00- x1F x7F      n     r         r n       r        r               lt  gt           x00- x1F x7F       n     r          r n       r        r               lt  gt           x00- x1F x7F       n     r          r n       r        r        I believe it s fully complient with RFC 822 including the errata  It only recognizes email addresses in their canonical form  For a regex that recognizes  folding  whitespace see the derivation below   The derivation shows how I arrived at the expression  I list all the relevant grammar rules from the RFC exactly as they appear  followed by the corresponding regex  Where an erratum has been published I give a separate expression for the corrected grammar rule  marked  erratum   and use the updated version as a subexpression in subsequent regular expressions   As stated in paragraph 3 1 4  of RFC 822 optional linear white space may be inserted between lexical tokens  Where applicable I ve expanded the expressions to accommodate this rule and marked the result with  opt-lwsp    CHAR            lt any ASCII character gt                    CTL             lt any ASCII control character and DEL gt                   x00- x1F x7F   CR              lt ASCII CR  carriage return gt                  r  LF              lt ASCII LF  linefeed gt                  n  SPACE           lt ASCII SP  space gt                    HTAB            lt ASCII HT  horizontal-tab gt                  t   lt   gt              lt ASCII quote mark gt                    CRLF           CR LF                 r n  LWSP-char      SPACE   HTAB                   t   linear-white-space    1   CRLF  LWSP-char                           r n     t     specials                     lt       gt                                     lt   gt                                          lt  gt            quoted-pair        CHAR                     qtext           lt any CHAR excepting  lt   gt        amp  CR  and including linear-white-space gt                       r     r n     t     dtext           lt any CHAR excluding                amp  CR   amp  including linear-white-space gt                        r     r n     t     quoted-string      lt   gt    qtext quoted-pair   lt   gt                            r     r n     t           erratum             n     r         r n       r    r n     t        r     domain-literal          dtext quoted-pair                                  r     r n     t           erratum              n     r          r n       r    r n     t        r     atom           1  lt any CHAR except specials  SPACE and CTLs gt                        lt  gt           x00- x1F x7F    word           atom   quoted-string                       lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r     domain-ref     atom  sub-domain     domain-ref   domain-literal                       lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r     local-part     word       word                         lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r               lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r        opt-lwsp              lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r        r n     t        r n     t           lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r        domain         sub-domain       sub-domain                         lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r               lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        opt-lwsp              lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        r n     t        r n     t           lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        addr-spec      local-part     domain                        lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r               lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r               lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r               lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        opt-lwsp              lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r       r n     t         r n     t           lt  gt           x00- x1F x7F      n     r         r n       r    r n     t        r       r n     t         r n     t           lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        r n     t        r n     t           lt  gt           x00- x1F x7F       n     r          r n       r    r n     t        r        canonical             lt  gt           x00- x1F x7F      n     r         r n       r        r               lt  gt           x00- x1F x7F      n     r         r n       r        r               lt  gt           x00- x1F x7F       n     r          r n       r        r               lt  gt           x00- x1F x7F       n     r          r n       r        r         RFC 5322  I arrived at the following regular expression  I invite everyone to try and break it  If you find any false positives or false negatives  please post them in a comment and I ll try to fix the expression as soon as possible     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          -  -    -9  A-Z -       -  -    -9  A-Z -          t -Z -       I believe it s fully complient with RFC 5322 including the errata  It only recognizes email addresses in their canonical form  For a regex that recognizes  folding  whitespace see the derivation below   The derivation shows how I arrived at the expression  I list all the relevant grammar rules from the RFC exactly as they appear  followed by the corresponding regex  For rules that include semantically irrelevant  folding  whitespace  I give a separate regex marked   normalized   that doesn t accept this whitespace   I ignored all the  obs-  rules from the RFC  This means that the regexes only match email addresses that are strictly RFC 5322 compliant  If you have to match  old  addresses  as the looser grammar including the  obs-  rules does   you can use one of the RFC 822 regexes from the previous paragraph   VCHAR                x21-7E                       -    ALPHA                x41-5A    x61-7A                      A-Za-z   DIGIT                x30-39                      0-9   HTAB                 x09                      t  CR                   x0D                      r  LF                   x0A                      n  SP                   x20                       DQUOTE               x22                        CRLF                CR LF                      r n  WSP                 SP   HTAB                       t    quoted-pair              VCHAR   WSP                          t -    FWS                    WSP CRLF  1 WSP                         t    r n    t     ctext                d33-39    d42-91    d93-126                        -  -  -      comment  is left out in the regex  ccontent            ctext   quoted-pair   comment                        -  -  -        t -      not regular  comment                    FWS  ccontent   FWS        is equivalent to FWS when leaving out comments  CFWS                 1   FWS  comment   FWS     FWS                        t    r n    t     atext               ALPHA   DIGIT                             amp                        -                                                                                   -  -    -9  A-Z -    dot-atom-text       1 atext       1 atext                       -  -    -9  A-Z -       -  -    -9  A-Z -       dot-atom             CFWS  dot-atom-text  CFWS                          t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t       normalized          -  -    -9  A-Z -       -  -    -9  A-Z -       qtext                d33    d35-91    d93-126                         -  -    qcontent            qtext   quoted-pair                         -  -        t -      erratum  quoted-string        CFWS  DQUOTE   1   FWS  qcontent   FWS     FWS  DQUOTE  CFWS                          t    r n    t            t    r n    t          -  -        t -          t    r n    t          t    r n    t           t    r n    t       normalized               -  -   t       t -        dtext                d33-90    d94-126                       -Z -    domain-literal       CFWS         FWS  dtext   FWS       CFWS                          t    r n    t            t    r n    t       -Z -        t    r n    t          t    r n    t       normalized             t -Z -      local-part          dot-atom   quoted-string                         t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t          t    r n    t            t    r n    t          -  -        t -          t    r n    t          t    r n    t           t    r n    t       normalized          -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -        domain              dot-atom   domain-literal                         t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t          t    r n    t            t    r n    t       -Z -        t    r n    t          t    r n    t       normalized          -  -    -9  A-Z -       -  -    -9  A-Z -          t -Z -      addr-spec           local-part     domain                          t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t          t    r n    t            t    r n    t          -  -        t -          t    r n    t          t    r n    t           t    r n    t            t    r n    t      -  -    -9  A-Z -       -  -    -9  A-Z -         t    r n    t          t    r n    t            t    r n    t       -Z -        t    r n    t          t    r n    t        normalized           -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          -  -    -9  A-Z -       -  -    -9  A-Z -          t -Z -        Note that some sources  notably w3c  claim that RFC 5322 is too strict on the local part  i e  the part before the  -sign   This is because        a  b  and  a   are not valid dot-atoms  while they may be used as mailbox names  The RFC  however  does allow for local parts like these  except that they have to be quoted  So instead of a  b example net you should write  a  b  example net  which is semantically equivalent   Further restrictions  SMTP  as defined in RFC 5321  further restricts the set of valid email addresses  or actually  mailbox names   It seems reasonable to impose this stricter grammar  so that the matched email address can actually be used to send an email   RFC 5321 basically leaves alone the  local  part  i e  the part before the  -sign   but is stricter on the domain part  i e  the part after the  -sign   It allows only host names in place of dot-atoms and address literals in place of domain literals   The grammar presented in RFC 5321 is too lenient when it comes to both host names and IP addresses  I took the liberty of  correcting  the rules in question  using this draft and RFC 1034 as guidelines  Here s the resulting regex     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z          25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3  IPv6     0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3           IPv6   0-9A-Za-z-   0-9A-Za-z    -Z -        Note that depending on the use case you may not want to allow for a  General-address-literal  in your regex  Also note that I used a negative lookahead    IPv6   in the final regex to prevent the  General-address-literal  part to match malformed IPv6 addresses  Some regex processors don t support negative lookahead  Remove the substring     IPv6   0-9A-Za-z-   0-9A-Za-z    -Z -    from the regex if you want to take the whole  General-address-literal  part out   Here s the derivation   Let-dig             ALPHA   DIGIT                      0-9A-Za-z   Ldh-str                ALPHA   DIGIT    -    Let-dig                      0-9A-Za-z-   0-9A-Za-z    regex is updated to make sure sub-domains are max  63 charactes long - RFC 1034 section 3 5  sub-domain          Let-dig  Ldh-str                       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z     Domain              sub-domain       sub-domain                       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       Snum                1 3DIGIT                      0-9  1 3    suggested replacement for  Snum   ip4-octet           DIGIT    x31-39 DIGIT    1  2DIGIT    2   x30-34 DIGIT    25   x30-35                     25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9   IPv4-address-literal        Snum 3      Snum                               0-9  1 3     0-9  1 3   3    suggested replacement for  IPv4-address-literal   ip4-address         ip4-octet 3     ip4-octet                       25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3    suggested replacement for  IPv6-hex   ip6-h16              0        x49-57    x65-70   x97-102  0 3  x48-57    x65-70   x97-102                        0  1-9A-Fa-f  0-9A-Fa-f  0 3    not from RFC  ls32                ip6-h16     ip6-h16   ip4-address                      0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3    suggested replacement of  IPv6-addr   ip6-address                                            6 ip6-h16      ls32                                                        5 ip6-h16      ls32                                         ip6-h16        4 ip6-h16      ls32                          1 ip6-h16      ip6-h16        3 ip6-h16      ls32                          2 ip6-h16      ip6-h16        2 ip6-h16      ls32                          3 ip6-h16      ip6-h16          ip6-h16      ls32                          4 ip6-h16      ip6-h16                       ls32                          5 ip6-h16      ip6-h16          ip6-h16                          6 ip6-h16      ip6-h16                               0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3        IPv6-address-literal         IPv6   ip6-address                             IPv6     0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3         Standardized-tag            Ldh-str                              0-9A-Za-z-   0-9A-Za-z   dcontent             d33-90    d94-126                       -Z -    General-address-literal     Standardized-tag     1 dcontent                              0-9A-Za-z-   0-9A-Za-z    -Z -     address-literal           IPv4-address-literal   IPv6-address-literal   General-address-literal                               25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3  IPv6     0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3           IPv6   0-9A-Za-z-   0-9A-Za-z    -Z -       Mailbox             Local-part       Domain   address-literal                         -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z          25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3  IPv6     0  1-9A-Fa-f  0-9A-Fa-f  0 3     6      0  1-9A-Fa-f  0-9A-Fa-f  0 3     5   0-9A-Fa-f  0 4     0  1-9A-Fa-f  0-9A-Fa-f  0 3     4     0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     3     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 2  0  1-9A-Fa-f  0-9A-Fa-f  0 3        0  1-9A-Fa-f  0-9A-Fa-f  0 3     2     0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 3  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 4  0  1-9A-Fa-f  0-9A-Fa-f  0 3         0  1-9A-Fa-f  0-9A-Fa-f  0 3    0  1-9A-Fa-f  0-9A-Fa-f  0 3    25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9      25 0-5  2 0-4  0-9  1 0-9  2   1-9   0-9    3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 5  0  1-9A-Fa-f  0-9A-Fa-f  0 3       0  1-9A-Fa-f  0-9A-Fa-f  0 3      0  1-9A-Fa-f  0-9A-Fa-f  0 3     0 6  0  1-9A-Fa-f  0-9A-Fa-f  0 3           IPv6   0-9A-Za-z-   0-9A-Za-z    -Z -         User input validation  A common use case is user input validation  for example on an html form  In that case it s usually reasonable to preclude address-literals and to require at least two labels in the hostname  Taking the improved RFC 5321 regex from the previous section as a basis  the resulting expression would be     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -         0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z       I do not recommend restricting the local part further  e g  by precluding quoted strings  since we don t know what kind of mailbox names some hosts allow  like  a  b  example net or even  a b  example net    I also do not recommend explicitly validating against a list of literal top-level domains or even imposing length-constraints  remember how   museum  invalidated  a-z  2 4    but if you must     -  -    -9  A-Z -       -  -    -9  A-Z -            -  -   t       t -          0-9A-Za-z   0-9A-Za-z-  0 61  0-9A-Za-z        net org com info etc      Make sure to keep your regex up-to-date if you decide to go down the path of explicit top-level domain validation   Further considerations  When only accepting host names in the domain part  after the  -sign   the regexes above accept only labels with at most 63 characters  as they should  However  they don t enforce the fact that the entire host name must be at most 253 characters long  including the dots   Although this constraint is strictly speaking still regular  it s not feasible to make a regex that incorporates this rule   Another consideration  especially when using the regexes for input validation  is feedback to the user  If a user enters an incorrect address  it would be nice to give a little more feedback than a simple  syntactically incorrect address   With  vanilla  regexes this is not possible   These two considerations could be addressed by parsing the address  The extra length constraint on host names could in some cases also be addressed by using an extra regex that checks it  and matching the address against both expressions   None of the regexes in this answer are optimized for performance  If performance is an issue  you should see if  and how  the regex of your choice can be optimized

User · Answer

public bool ValidateEmail string sEmail        if  sEmail    null                return false             int nFirstAT   sEmail IndexOf           int nLastAT   sEmail LastIndexOf            if   nFirstAT  gt  0   amp  amp   nLastAT    nFirstAT   amp  amp   nFirstAT  lt   sEmail Length - 1                  return  Regex IsMatch sEmail      a-z 0-9 A-Z       a-z 0-9 A-Z         a-z 0-9 A-Z         a-z 0-9 A-Z          a-z 0-9 A-Z        a-z  a-z 0-9 A-Z      a-z  a-z 0-9 A-Z      a-z  a-z 0-9 A-Z                     else               return false

User · Answer

Java Mail API does magic for us      try            InternetAddress internetAddress   new InternetAddress email        internetAddress validate         return true            catch Exception ex                return false          I got this from here

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For the most comprehensive evaluation of the best regular expression for validating an email address please see this link   Comparing E-mail Address Validating Regular Expressions   Here is the current top expression for reference purposes        w         amp        -                         w         amp        -                          a-z0-9  1  a-z0-9 -  0 62  a-z0-9  1    a-z       a-z  2 6     d 1 3     3  d 1 3     d 1 5      i

User · Answer

I use    w   -     w     w   -   w      w   -   w       Which is the one used in ASP NET by the RegularExpressionValidator

User · Answer

If you need a simple form to validate  you can use the answer of https   regexr com 3e48o    w-        w-        w-  2 4

User · Answer

a-zA-Z0-9-       a-zA-Z0-9-      a-zA-Z0-9-      a-zA-Z0-9-         0-9  1 3     a-zA-Z  2 3    aero coop info museum name      This matches 99 99  of email addresses  including some of the newer top-level-domain extensions  such as info  museum  name  etc   It also allows for emails tied directly to IP addresses

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We have used http   www aspnetmx com  with a degree of success for a few years now  You can choose the level you want to validate at  e g  syntax check  check for the domain  mx records or the actual email    For front-end forms we generally verify that the domain exists and the syntax is correct  then we do stricter verification to clean out our database before doing bulk mail-outs

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Don t know about best  but this one is at least correct  as long as the addresses have their comments stripped and replaced with whitespace   Seriously  You should use an already written library for validating emails  The best way is probably to just send a verification e-mail to that address

User · Answer

this simple pattern works for me      lt name gt    lt  gt         s   quot   1       lt domain gt    lt  gt         s   quot   2       lt top gt    lt  gt          s   quot   2

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I   ve had a similar desire  wanting a quick check for syntax in eMail addresses without going overboard  the Mail  RFC822  Address answer which is the obviously correct one  for an eMail send utility  I went with this  I   m a POSIX RE person so I don   t normally use  d and such from PCRE  as they make things less legible to me    preg match     -  -    -9  A-Z -       -  -    -9  A-Z -       0-9A-Za-z   -0-9A-Za-z  0 61  0-9A-Za-z       0-9A-Za-z   -0-9A-Za-z  0 61  0-9A-Za-z            adr    This is RFC-correct but explicitly excludes the obsolete forms as well as direct IPs  IP and Legacy IP both   which someone in the target group of that utility  mostly  people who bother us in  sendmail on IRC  would not normally want or need anyway   IDNs  internationalised domain names  are explicitly not in the scope of eMail  addresses like    foo c  cilienchor-bonn de    must be written    foo xn--ccilienchor-bonn-vnb de    on the wire instead  this includes mailto  links in HTML and such fun   only the GUI is allowed to display  and accept then convert  such names to  and from  the user

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It all depends on how accurate you want to be   For my purposes  where I m just trying to keep out things like bob   aol com  spaces in emails  or steve  no domain at all  or mary aolcom  no period before  com   I use     S   S    S      Sure  it will match things that aren t valid email addresses  but it s a matter of getting common simple errors   There are any number of changes that can be made to that regex  and some are in the comments for this answer   but it s simple  and easy to understand  and is a fine first attempt

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For a vivid demonstration  the following monster is pretty good but still does not correctly recognize all syntactically valid email addresses  it recognizes nested comments up to four levels deep   This is a job for a parser  but even if an address is syntactically valid  it still may not be deliverable  Sometimes you have to resort to the hillbilly method of  Hey  y all  watch ee-us       derivative of work with the following copyright and license     Copyright  c  2004 Casey West   All rights reserved     This module is free software  you can redistribute it and or    modify it under the same terms as Perl itself      see http   search cpan org  cwest Email-Address-1 80   private static string gibberish        -xism      -xism   -xism   -xism   -xism   -xism   -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s    s      s      x00- x1F x7F   lt  gt            lt DQ gt  s    -xism   -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s    s      s       -xism   -xism   -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D      -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A x 0D         s    s       s    s     s    lt DQ gt   -xism   -xism       lt DQ gt      -xism     -xism    x0A x0D      lt DQ gt   -xism   -xi sm  s       s   -xism   -xism    gt              -xism     -xis m    x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s     s     s          -xism   -xism   -xism  s       s   -xism    -xism    gt              -xism     -xism    x0A x0D      -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D         s    s       s    s     s    lt   -xism   -xi sm   -xism   -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s    -xism   -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s     -xism    x00- x1F x7F   lt   gt            lt DQ gt  s          x00- x1F x7F   lt  gt            lt DQ gt  s        -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s   -xism    -xism    gt              -xism     -xism    x0A x0D         s     s       s    s     s       -xism   -xism   -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A x 0D      -xism  s       s   -xism   -xism    gt              -xi sm     -xism    x0A x0D         s    s       s    s     s     lt DQ gt   -xism   -xism      lt DQ gt      -xism     -xism    x0A x0D       lt DQ gt   -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s   -x ism   -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s         -xism   -xism   -xism    -xism  s       s   -xism   -xism    gt              -xism      -xism    x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s     s     s     -xism    x00- x1F x7F   lt  gt            lt DQ gt  s           x00- x1F x7F   lt  gt            lt DQ gt  s       -xism   -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s    s      s       -xism   -xism   -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D      -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A  x0D         s    s       s    s     s         s   -xism   -x ism              -xism     -xism    x0A x0D        s     -xi sm   -xism  s       s   -xism   -xism    gt              -xism      -xism    x0A x0D      -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D         s    s        s    s     s       gt   -xism   -xism  s       s   -xism   - xism    gt              -xism     -xism    x0A x0D      -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D         s    s       s    s     s        -xism   -x ism   -xism   -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s    -xism   -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s     -xism    x00- x1F x7F    lt  gt            lt DQ gt  s          x00- x1F x7F   lt  gt            lt DQ gt  s        -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s   -xism    -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s       -xism   -xism   -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A  x0D      -xism  s       s   -xism   -xism    gt              -x ism     -xism    x0A x0D         s    s       s    s     s     lt DQ gt   -xism   -xism      lt DQ gt      -xism     -xism    x0A x0D       lt DQ gt   -xism   -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D      -xism  s       s   - xism   -xism    gt              -xism     -xism    x0A x0D          s    s       s    s     s         -xism   -xism   -xism    -xism  s       s   -xism   -xism    gt              -xism      -xism    x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s        s    s     s     -xism    x00- x1F x7F   lt  gt            lt DQ gt  s           x00- x1F x7F   lt  gt            lt DQ gt  s       -xism   -xism   s       s   -xism   -xism    gt              -xism     -xism     x0A x0D      -xism  s       s   -xism   -xism    gt               -xism     -xism    x0A x0D         s    s       s    s      s       -xism   -xism   -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D      -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A  x0D         s    s       s    s     s         s   -xism   - xism              -xism     -xism    x0A x0D        s     -x ism   -xism  s       s   -xism   -xism    gt              -xism      -xism    x0A x0D      -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D         s    s        s    s     s         -xism  s       s   -xism   -xism     gt              -xism     -xism    x0A x0D      -xism  s        s   -xism   -xism    gt              -xism     -xism    x0A x0 D         s    s       s    s         Replace   lt DQ gt             Replace   t          Replace             Replace   r          Replace   n         private static Regex mailbox     new Regex gibberish  RegexOptions ExplicitCapture

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I ve been using this touched up version of your regex for a while and it hasn t left me with too many surprises  I ve never encountered an apostrophe in an email yet so it doesn t validate that  It does validate Jean Fran  ois anydomain museum and                      but not weird abuse of those non alphanumeric characters    you com            amp   -            w d  amp  -        w d  amp  -       w d-       w d-          d  1 3      w  2         It does support IP addresses you 192 168 1 1 but I haven t refined it enough to deal with bogus IP ranges such as 999 999 999 1   It also supports all the TLDs over 3 characters which stops asdf asdf asdf which I think the original let through  I ve been beat  there are too many tlds now over 3 characters   I know acrosman has abandoned his regex but this flavour lives on

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Although very detailed answers are already added  I think those are complex enough for a developer who is just looking for a simple method to validate an Email address or to get all Email Address From string in java   public static boolean isEmailValid  NonNull String email            return android util Patterns EMAIL ADDRESS matcher email  matches            As per the regular expression is concerned  I always use this regular expression  which works for my problems     A-Z0-9a-z    -    A-Za-z0-9 -     A-Za-z  2 6     If you are looking to find all email addresses from a String by matching email Regular Expression  You can find a method at this link

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For the most comprehensive evaluation of the best regular expression for validating an email address please see this link   Comparing E-mail Address Validating Regular Expressions   Here is the current top expression for reference purposes        w         amp        -                         w         amp        -                          a-z0-9  1  a-z0-9 -  0 62  a-z0-9  1    a-z       a-z  2 6     d 1 3     3  d 1 3     d 1 5      i

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While deciding which characters are allowed  please remember your apostrophed and hyphenated friends  I have no control over the fact that my company generates my email address using my name from the HR system  That includes the apostrophe in my last name  I can t tell you how many times I have been blocked from interacting with a website by the fact that my email address is  invalid

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It   s easy in Perl 5 10 or newer       DEFINE        lt address gt             amp mailbox       amp group         lt mailbox gt             amp name addr       amp addr spec         lt name addr gt           amp display name      amp angle addr         lt angle addr gt          amp CFWS    lt     amp addr spec   gt     amp CFWS          lt group gt               amp display name          amp mailbox list       amp CFWS                                                   amp CFWS          lt display name gt        amp phrase         lt mailbox list gt        amp mailbox           amp mailbox            lt addr spec gt           amp local part        amp domain         lt local part gt          amp dot atom       amp quoted string         lt domain gt              amp dot atom       amp domain literal         lt domain literal gt      amp CFWS             amp FWS      amp dcontent       amp FWS                                          amp CFWS          lt dcontent gt            amp dtext       amp quoted pair         lt dtext gt               amp NO WS CTL      x21- x5a x5e- x7e          lt atext gt               amp ALPHA       amp DIGIT           amp    -                   lt atom gt                amp CFWS      amp atext      amp CFWS          lt dot atom gt            amp CFWS      amp dot atom text     amp CFWS          lt dot atom text gt       amp atext             amp atext             lt text gt               x01- x09 x0b x0c x0e- x7f         lt quoted pair gt            amp text          lt qtext gt               amp NO WS CTL      x21 x23- x5b x5d- x7e         lt qcontent gt            amp qtext       amp quoted pair         lt quoted string gt       amp CFWS      amp DQUOTE        amp FWS      amp qcontent                               amp FWS      amp DQUOTE     amp CFWS           lt word gt                amp atom       amp quoted string         lt phrase gt              amp word          Folding white space       lt FWS gt                     amp WSP      amp CRLF       amp WSP          lt ctext gt               amp NO WS CTL      x21- x27 x2a- x5b x5d- x7e         lt ccontent gt            amp ctext       amp quoted pair       amp comment         lt comment gt                    amp FWS      amp ccontent       amp FWS              lt CFWS gt                    amp FWS      amp comment                                     amp FWS      amp comment        amp FWS          No whitespace control       lt NO WS CTL gt          x01- x08 x0b x0c x0e- x1f x7f          lt ALPHA gt             A-Za-z         lt DIGIT gt             0-9         lt CRLF gt              x0d  x0a        lt DQUOTE gt                    lt WSP gt                x20 x09           amp address  x

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No one mentioned the issue of localization  i18   what if you have clients coming from all over the world  You will need to then need to sub-categorize your regex per country area  which I have seen developers ending up building a large dictionary config  Detecting users  browser language setting may be a good starting point

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The regular expression for an email address is      quot       -    - u 10FFFF       t - u 10FFFF     quot     -    - -9  A-Z  - u 10FFFF           -    - -9  A-Z  - u 10FFFF          -    - -9  A-Z  - u 10FFFF           -    - -9  A-Z  - u 10FFFF         -Z  - u 10FFFF        u  This regular expression is 100  identical to the addr-spec ABNF for non-obsolete email addresses  as specified across RFC 5321  RFC 5322  and RFC 6532  Additionally  you must verify   The email address is well-formed UTF-8  or ASCII  if you cannot send to internationalized email addresses  The address is not more than 320 UTF-8 bytes The user part  the first match group  is not more than 64 UTF-8 bytes The domain part  the second match group  is not more than 255 UTF-8 bytes  The easiest way to do all of this is to use an existing function  In PHP  see the filter var function using FILTER VALIDATE EMAIL and FILTER FLAG EMAIL UNICODE  if you can send to internationalized email addresses    email valid   filter var  email input  FILTER VALIDATE EMAIL  FILTER FLAG EMAIL UNICODE    However  maybe you re building such a function   indeed the easiest way to implement this is to use a regular expression  Remember  this only verifies that the email address will not cause a syntax error  The only way to verify that the address can receive email is to actually send an email  Next  I will treat how you generate this regular expression   I write a new answer  because most of the answers here make the mistake of either specifying a pattern that is too restrictive  and so have not aged well   or they present a regular expression that s actually matching a header for a MIME message  and not the email address itself  It is entirely possible to make a regular expression from an ABNF  so long as there are no recursive parts  RFC 5322 specifies what is legal to send in a MIME message  consider this the upper bound on what is a legal email address  However  to follow this ABNF exactly would be a mistake  this pattern technically represents how you encode an email address in a MIME message  and allows strings not part of the email address  like folding whitespace and comments  and it includes support for obsolete forms that are not legal to generate  but that servers read for historical reasons    An email address does not include these  RFC 5322 explains   Both atom and dot-atom are interpreted as a single unit  comprising the string of characters that make it up   Semantically  the optional comments and FWS surrounding the rest of the characters are not part of the atom  the atom is only the run of atext characters in an atom  or the atext and  quot   quot  characters in a dot-atom    In some of the definitions  there will be non-terminals whose names start with  quot obs- quot    These  quot obs- quot  elements refer to tokens defined in the obsolete syntax in section 4   In all cases  these productions are to be ignored for the purposes of generating legal Internet messages and MUST NOT be used as part of such a message   If you remove CFWS  BWS  and obs-  rules from the addr-spec in RFC 5322  and perform some optimization on the result  I used  quot greenery quot    you can produce this regular expression  quoted with slashes and anchored  suitable for use in ECMAScript and compatible dialects  with added newline for clarity       quot       -    -       t -     quot     -    - -9  A-Z  -           -    - -9  A-Z  -           -    - -9  A-Z  -           -    - -9  A-Z  -         -Z  -          This only supports ASCII email addresses  To support RFC 6532 Internationalized Email Addresses  replace the   character with  u 10FFFF   PHP  ECMAScript with the u flag   or  uFFFF  for UTF-16 implementations  like  Net and older ECMAScript JavaScript       quot       -    - u 10FFFF       t - u 10FFFF     quot     -    - -9  A-Z  - u 10FFFF           -    - -9  A-Z  - u 10FFFF          -    - -9  A-Z  - u 10FFFF           -    - -9  A-Z  - u 10FFFF         -Z  - u 10FFFF        u  This works because the ABNF we are using is not recursive  and so forms a non-recursive  regular grammar that can be converted into a regular expression  It breaks down like so   The user part  before the    may be a dot-atom or a quoted-string  quot     -    -       t -     quot  specifies the quoted-string form of the user  e g   quot root home quot  example com  It permits any non-control character inside double quotes  except that spaces  tabs  doublequotes  and backslashes must be backslash-escaped     -    - -9  A-Z  -   is the first character of the dot-atom of the user         -    - -9  A-Z  -     matches the rest of the dot-atom  allowing dots  except after another dot  or as the final character     denotes the domain  The domain part may be a dot-atom or a domain-literal     -    - -9  A-Z  -         -    - -9  A-Z  -     is the same dot-atom form as above  but here it represents domain names and IPv4 addresses      -Z  -      will match IPv6 addresses and future definitions of host names   This RegExp allows all spec-compliant email addresses  and can be used verbatim in a MIME message  except for line length limits  in which case folding whitespace must be added   This also sets non-capturing groups such that match 1  will be the user  match 2  will be the host   However if match 1  starts with a double quote  then filter out backslash escapes  and the start and end double quotes   quot root quot  example com and root example com identify the same inbox   Finally  note that RFC 5321 sets limits on how long an email address may be  The user part may be up to 64 bytes  and the domain part may be up to 255 bytes  Including the   character  the limit for the entire address is 320 bytes  This is measured in bytes after the address is UTF-8 encoded  not characters  Note that RFC 5322 ABNF defines a permissive syntax for domain names  allowing names currently known to be invalid  This also allows for domain names that could become legal in the future  This should not be a problem  as this should be handled the same way a non-existent domain name is  Always consider the possibility that a user typed in an email address that works  but that they do not have access to  The only foolproof way to verify an email address is to send an email  This is adapted from my article E-Mail Addresses  amp  Syntax

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I never bother creating with my own regular expression  because chances are that someone else has already come up with a better version   I always use regexlib to find one to my liking

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You can use following regular Expression for any email address        lt  gt             s           lt  gt             s                        0-9  1 3    0-9  1 3    0-9  1 3    0-9  1 3        a-zA-Z -0-9       a-zA-Z  2        For PHP    function checkEmailValidation  email                       expression         lt  gt             s           lt  gt             s                        0-9  1 3    0-9  1 3    0-9  1 3    0-9  1 3        a-zA-Z -0-9       a-zA-Z  2                 if preg match  expression   email                         return true           else                       return false                   For Javascript   function checkEmailValidation email                       var pattern         lt  gt             s           lt  gt             s                        0-9  1 3    0-9  1 3    0-9  1 3    0-9  1 3        a-zA-Z -0-9       a-zA-Z  2                 if pattern test email                         return true           else                       return false

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hmm strange not to see this answer already within the answers  Here is the one I ve build  It is not a bulletproof version but it is  simple  and checks almost everything     w -         w -       w -         w -          a-zA-Z  2 4     I think an explanation is in place so you can modify it if you want    e     w -   matches a-z  A-Z        - at least one time    m          w -     matches a-z  A-Z        - zero or more times but need to start with a    dot            i     w -   matches a-z  A-Z        - at least one time    l          w -     matches a-z  A-Z        - zero or more times but need to start with a    dot     com         a-zA-Z  2 4   matches a-z  A-Z for 2 to 4 times starting with a    dot   giving e  m  i  l  com where   m  and   l  are optional but also can be repeated multiple times  I think this validates all valid email addresses but blocks potential invalid without using an over complex regular expression which won t be necessary in most cases   notice this will allow   - com but that is the compromise for keeping it simple

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A regex that does exactly what the standards say is allowed  according to what I ve seen about them  is this            -        -        2         254       a-z xC0- xFF0-9     amp                -         253         -     -     a-z0-9-  1 63      a-z  2 63     01   0-9  2  2  0-4  0-9  5 0-5    0-9      3   01   0-9  2  2  0-4  0-9  5 0-5    0-9     gim   Demo   Debuggex analysis  interactive   Split up           -        -        2         254        a-z xC0- xFF0-9     amp                -          253               -     -          a-z0-9-  1 63           a-z  2 63               01   0-9  2  2  0-4  0-9  5 0-5    0-9      3        01   0-9  2  2  0-4  0-9  5 0-5    0-9        Analysis          -        -        2         254        Negative lookahead for either an address starting with a    ending with one  having    in it  or exceeding the 254 character max length      a-z xC0- xFF0-9     amp                -       matching 1 or more of the permitted characters  with the negative look applying to it         253        Negative lookahead for the domain name part  restricting it to 253 characters in total       -     -      Negative lookahead for each of the domain names  which are don t allow starting or ending with        a-z0-9-  1 63        simple group match for the allowed characters in a domain name  which are limited to 63 characters each     a-zA-Z  2 63    simple group match for the allowed top-level domain  which currently still is restricted to letters only  but does include  4 letter TLDs        01   0-9  2  2  0-4  0-9  5 0-5    0-9      3    01   0-9  2  2  0-4  0-9  5 0-5    0-9     the alternative for domain names  this matches the first 3 numbers in an IP address with a   behind it  and then the fourth number in the IP address without   behind it

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Strange that you  cannot  allow 4 characters TLDs   You are banning people from  info and  name  and the length limitation stop  travel and  museum  but yes  they are less common than 2 characters TLDs and 3 characters TLDs   You should allow uppercase alphabets too   Email systems will normalize the local part and domain part   For your regex of domain part  domain name cannot starts with  -  and cannot ends with  -   Dash can only stays in between   If you used the PEAR library  check out their mail function  forgot the exact name library    You can validate email address by calling one function  and it validates the email address according to definition in RFC822

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Here s the PHP I use  I ve choosen this solution in the spirit of  false positives are better than false negatives  as declared by another commenter here AND with regards to keeping your response time up and server load down     there s really no need to waste server resources with a regular expression when this will weed out most simple user error  You can always follow this up by sending a test email if you want   function validateEmail  email      return  bool  stripos  email

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I m still using     A-Za-z0-9    -      A-Za-z0-9  -     A-Za-z  2      But with IPv6 and Unicode coming up  perhaps     w    s       s  2      is best  Gmail already allows sequential dots  but Microsoft Exchange Server 2007 refuses them

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I don t believe the claim made by bortzmeyer  above  that  The grammar  specified in RFC 5322  is too complicated for that   to be handled by a regular expression    Here is the grammar   from http   tools ietf org html rfc5322 section-3 4 1   addr-spec           local-part     domain local-part          dot-atom   quoted-string   obs-local-part domain              dot-atom   domain-literal   obs-domain domain-literal       CFWS         FWS  dtext   FWS       CFWS  dtext                d33-90              Printable US-ASCII                      d94-126              characters not including                     obs-dtext                       or       Assuming that dot-atom  quoted-string  obs-local-part  obs-domain are themselves regular languages  this is a very simple grammar  Just replace the local-part and domain in the addr-spec production with their respective productions  and you have a regular language  directly translatable to a regular expression

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If you want to improve on a regex that has been working reasonably well over several years  then the answer depends on what exactly you want to achieve - what kinds of email addresses have been failing  Fine-tuning email regexes is very difficult  and I have yet to see a perfect solution    If your application involves something very technical in nature  or something internal to organizations   then maybe you need to support IP addresses instead of domain names  or comments in the  local  part of the email address  If your application is multinational  I would consider focusing on Unicode UTF8 support    The leading answer to your question currently links to a  fully RFC-822   compliant regex   However  in spite of the complexity of that regex and its presumed attention to detail in RFC rules  it completely fails when it comes to Unicode support   The regex that I ve written for most of my apps focuses on Unicode support  as well as reasonably good overall adherence to RFC standards                    2   a-zA-Z0-9 u0080- u00FF u0100- u017F u0180- u024F u0250- u02AF u0300- u036F u0370- u03FF u0400- u04FF u0500- u052F u0530- u058F u0590- u05FF u0600- u06FF u0700- u074F u0750- u077F u0780- u07BF u07C0- u07FF u0900- u097F u0980- u09FF u0A00- u0A7F u0A80- u0AFF u0B00- u0B7F u0B80- u0BFF u0C00- u0C7F u0C80- u0CFF u0D00- u0D7F u0D80- u0DFF u0E00- u0E7F u0E80- u0EFF u0F00- u0FFF u1000- u109F u10A0- u10FF u1100- u11FF u1200- u137F u1380- u139F u13A0- u13FF u1400- u167F u1680- u169F u16A0- u16FF u1700- u171F u1720- u173F u1740- u175F u1760- u177F u1780- u17FF u1800- u18AF u1900- u194F u1950- u197F u1980- u19DF u19E0- u19FF u1A00- u1A1F u1B00- u1B7F u1D00- u1D7F u1D80- u1DBF u1DC0- u1DFF u1E00- u1EFF u1F00- u1FFFu20D0- u20FF u2100- u214F u2C00- u2C5F u2C60- u2C7F u2C80- u2CFF u2D00- u2D2F u2D30- u2D7F u2D80- u2DDF u2F00- u2FDF u2FF0- u2FFF u3040- u309F u30A0- u30FF u3100- u312F u3130- u318F u3190- u319F u31C0- u31EF u31F0- u31FF u3200- u32FF u3300- u33FF u3400- u4DBF u4DC0- u4DFF u4E00- u9FFF uA000- uA48F uA490- uA4CF uA700- uA71F uA800- uA82F uA840- uA87F uAC00- uD7AF uF900- uFAFF       amp    -           - d            a-zA-Z0-9 u0080- u00FF u0100- u017F u0180- u024F u0250- u02AF u0300- u036F u0370- u03FF u0400- u04FF u0500- u052F u0530- u058F u0590- u05FF u0600- u06FF u0700- u074F u0750- u077F u0780- u07BF u07C0- u07FF u0900- u097F u0980- u09FF u0A00- u0A7F u0A80- u0AFF u0B00- u0B7F u0B80- u0BFF u0C00- u0C7F u0C80- u0CFF u0D00- u0D7F u0D80- u0DFF u0E00- u0E7F u0E80- u0EFF u0F00- u0FFF u1000- u109F u10A0- u10FF u1100- u11FF u1200- u137F u1380- u139F u13A0- u13FF u1400- u167F u1680- u169F u16A0- u16FF u1700- u171F u1720- u173F u1740- u175F u1760- u177F u1780- u17FF u1800- u18AF u1900- u194F u1950- u197F u1980- u19DF u19E0- u19FF u1A00- u1A1F u1B00- u1B7F u1D00- u1D7F u1D80- u1DBF u1DC0- u1DFF u1E00- u1EFF u1F00- u1FFF u20D0- u20FF u2100- u214F u2C00- u2C5F u2C60- u2C7F u2C80- u2CFF u2D00- u2D2F u2D30- u2D7F u2D80- u2DDF u2F00- u2FDF u2FF0- u2FFF u3040- u309F u30A0- u30FF u3100- u312F u3130- u318F u3190- u319F u31C0- u31EF u31F0- u31FF u3200- u32FF u3300- u33FF u3400- u4DBF u4DC0- u4DFF u4E00- u9FFF uA000- uA48F uA490- uA4CF uA700- uA71F uA800- uA82F uA840- uA87F uAC00- uD7AF uF900- uFAFF -   d         a-zA-Z u0080- u00FF u0100- u017F u0180- u024F u0250- u02AF u0300- u036F u0370- u03FF u0400- u04FF u0500- u052F u0530- u058F u0590- u05FF u0600- u06FF u0700- u074F u0750- u077F u0780- u07BF u07C0- u07FF u0900- u097F u0980- u09FF u0A00- u0A7F u0A80- u0AFF u0B00- u0B7F u0B80- u0BFF u0C00- u0C7F u0C80- u0CFF u0D00- u0D7F u0D80- u0DFF u0E00- u0E7F u0E80- u0EFF u0F00- u0FFF u1000- u109F u10A0- u10FF u1100- u11FF u1200- u137F u1380- u139F u13A0- u13FF u1400- u167F u1680- u169F u16A0- u16FF u1700- u171F u1720- u173F u1740- u175F u1760- u177F u1780- u17FF u1800- u18AF u1900- u194F u1950- u197F u1980- u19DF u19E0- u19FF u1A00- u1A1F u1B00- u1B7F u1D00- u1D7F u1D80- u1DBF u1DC0- u1DFF u1E00- u1EFF u1F00- u1FFF u20D0- u20FF u2100- u214F u2C00- u2C5F u2C60- u2C7F u2C80- u2CFF u2D00- u2D2F u2D30- u2D7F u2D80- u2DDF u2F00- u2FDF u2FF0- u2FFF u3040- u309F u30A0- u30FF u3100- u312F u3130- u318F u3190- u319F u31C0- u31EF u31F0- u31FF u3200- u32FF u3300- u33FF u3400- u4DBF u4DC0- u4DFF u4E00- u9FFF uA000- uA48F uA490- uA4CF uA700- uA71F uA800- uA82F uA840- uA87F uAC00- uD7AF uF900- uFAFF   2 63      i   I ll avoid copy-pasting complete answers  so I ll just link this to a similar answer I provided here  How to validate a unicode email   There is also a live demo available for the regex above at  http   jsfiddle net aossikine qCLVH 3

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For PHP I m using email address validator from Nette Framework - http   api nette org 2 3 3 source-Utils Validators php html 234-247     public static    function isEmail  value         atom     -a-z0-9     amp                     RFC 5322 unquoted characters in local-part      localPart                 x23-  x5B  x5D-  x7E         -        atom        atom          quoted or unquoted      alpha    a-z x80- xFF      superset of IDN      domain     0-9 alpha     -0-9 alpha  0 61  0-9 alpha         RFC 1034 one domain component      topDomain      alpha     -0-9 alpha  0 17   alpha          return  bool  preg match     localPart     domain      topDomain  z i    value

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There is not one which is really usable  I discuss some issues in my answer to Is there a php library for email address validation   it is discussed also in Regexp recognition of email address hard   In short  don t expect a single  usable regex to do a proper job  And the best regex will validate the syntax  not the validity of an e-mail  jhohn example com is correct but it will probably bounce

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This question is asked a lot  but I think you should step back and ask yourself why you want to validate email adresses syntactically  What is the benefit really    It will not catch common typos  It does not prevent people from entering invalid or made-up email addresses  or entering someone else s address     If you want to validate that an email is correct  you have no choice than to send an confirmation email and have the user reply to that  In many cases you will have to send a confirmation mail anyway for security reasons or for ethical reasons  so you cannot e g  sign someone up to a service against their will

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I   ve had a similar desire  wanting a quick check for syntax in eMail addresses without going overboard  the Mail  RFC822  Address answer which is the obviously correct one  for an eMail send utility  I went with this  I   m a POSIX RE person so I don   t normally use  d and such from PCRE  as they make things less legible to me    preg match     -  -    -9  A-Z -       -  -    -9  A-Z -       0-9A-Za-z   -0-9A-Za-z  0 61  0-9A-Za-z       0-9A-Za-z   -0-9A-Za-z  0 61  0-9A-Za-z            adr    This is RFC-correct but explicitly excludes the obsolete forms as well as direct IPs  IP and Legacy IP both   which someone in the target group of that utility  mostly  people who bother us in  sendmail on IRC  would not normally want or need anyway   IDNs  internationalised domain names  are explicitly not in the scope of eMail  addresses like    foo c  cilienchor-bonn de    must be written    foo xn--ccilienchor-bonn-vnb de    on the wire instead  this includes mailto  links in HTML and such fun   only the GUI is allowed to display  and accept then convert  such names to  and from  the user

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There are now many more  1000s  of TLD s  Most of the answers in here need to be voted down as they are no longer correct - potentially this question should have a 2nd edition   Feel free to visit a more current discussion on other post

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We have used http   www aspnetmx com  with a degree of success for a few years now  You can choose the level you want to validate at  e g  syntax check  check for the domain  mx records or the actual email    For front-end forms we generally verify that the domain exists and the syntax is correct  then we do stricter verification to clean out our database before doing bulk mail-outs

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You should not use regular expressions to validate email addresses   Instead  use the MailAddress class  like this   try       address   new MailAddress address  Address    catch FormatException           address is invalid     The MailAddress class uses a BNF parser to validate the address in full accordance with RFC822   If you plan to use the MailAddress to validate the e-mail address  be aware that this approach accepts the display name part of the e-mail address as well  and that may not be exactly what you want to achieve  For example  it accepts these strings as valid e-mail addresses     user1 hotmail com  user2 gmail com   user1 hotmail com  user2 gmail com  user3 company com   User Display Name user3 company com   user4  company com    In some of these cases  only the last part of the strings is parsed as the address  the rest before that is the display name  To get a plain e-mail address without any display name  you can check the normalized address against your original string   bool isValid   false   try       MailAddress address   new MailAddress emailAddress       isValid    address Address    emailAddress          or        isValid   string IsNullOrEmpty address DisplayName     catch  FormatException           address is invalid     Furthermore  an address having a dot at the end  like user company  is accepted by MailAddress as well   If you really want to use a regex  here it is                  r n     t                 lt  gt               000- 031            r n     t      Z           lt  gt                          r               r n     t             r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n      t            r n     t              r n     t           lt  gt               000- 0 31            r n     t     Z           lt  gt                           r                   r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t               lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n      t       lt        r n     t               lt  gt               000- 031             r n     t     Z           lt  gt                           r                  r n      t                r n     t           lt  gt               000- 031            r n      t     Z           lt  gt                           r                  r n     t                   r n     t           lt  gt               000- 031            r n      t     Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t             lt  gt               000- 031            r n     t      Z           lt  gt                          r               r n     t            r  n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n     t             r n     t              r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t        gt        r n     t             lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n      t            r n     t             r n     t                 lt  gt                000- 031            r n     t     Z           lt  gt                          r                r 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            r                  r n     t                  r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                           r                   r n     t                r n     t             lt  gt               0 00- 031            r n     t     Z           lt  gt                          r                r n     t            r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t              r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t        gt        r n     t         s             lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n     t               r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t       lt        r n      t               lt  gt               000- 031            r n     t     Z            lt  gt                           r                  r n     t                r n      t           lt  gt               000- 031            r n     t     Z           lt  gt                             r                  r n     t                  r n      t           lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t              lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n     t               r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                           r                  r n     t        gt         r n     t          s

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List item  I use this function   function checkmail  value            value   trim  value           if  stristr  value                    amp  amp  stristr  value                    amp  amp   strrpos  value       - stripos  value        gt  2                amp  amp   stripos  value        gt  1                amp  amp   strlen  value  - strrpos  value        lt  6                amp  amp   strlen  value  - strrpos  value        gt  2                amp  amp    value    preg replace               value                 amp  amp    value    preg replace     A-Za-z0-9 -               value                        else              return  Invalid Mail-Id

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this is one of the  regex for email       a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF        a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x22      x20  x09    x0d x0a     x20  x09        x01- x08 x0b x0c x0e- x1f x7f   x21   x23- x5b    x5d- x7e    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF         x01- x09 x0b x0c x0d- x7f    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x20  x09    x0d x0a     x20  x09      x22        a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF           a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF

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This question is asked a lot  but I think you should step back and ask yourself why you want to validate email adresses syntactically  What is the benefit really    It will not catch common typos  It does not prevent people from entering invalid or made-up email addresses  or entering someone else s address     If you want to validate that an email is correct  you have no choice than to send an confirmation email and have the user reply to that  In many cases you will have to send a confirmation mail anyway for security reasons or for ethical reasons  so you cannot e g  sign someone up to a service against their will

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According to RFC 2821 and RFC 2822  the local-part of an email addresses may use any of these ASCII characters     Uppercase and lowercare letters The digits 0 through 9  The characters       amp    -            The character     provided that it is not the first or last character in the local-part    Matches     a amp d somedomain com a d somedomain com a d somedomain com   Non-Matches     abc somedomain com abc  somedomain com a b somedomain com   For one that is RFC 2821  2822 Compliant you can use             amp     -           w          amp     -           w       amp     -             w  0        amp     -           w       w   -   w      w   -   w        Email - RFC 2821  2822 Compliant

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This question is asked a lot  but I think you should step back and ask yourself why you want to validate email adresses syntactically  What is the benefit really    It will not catch common typos  It does not prevent people from entering invalid or made-up email addresses  or entering someone else s address     If you want to validate that an email is correct  you have no choice than to send an confirmation email and have the user reply to that  In many cases you will have to send a confirmation mail anyway for security reasons or for ethical reasons  so you cannot e g  sign someone up to a service against their will

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I know this question is about RegEx  but guessing that 90  of all developers reading these solutions are trying to validate an E-Mail address in an HTML form displayed in a browser    If this is the case  I d suggest checking out the new HTML5  lt input type  email  gt  form element   HTML5     lt input type  email  required   gt    CSS3    input required         background-color  rgba 255 0 0 0 2        input focus invalid         box-shadow  0 0 1em red       border-color  red       input focus valid         box-shadow  0 0 1em green       border-color  green       http   jsfiddle net mYRe7 1  This has a couple of advantages    Automatic validation  no custom solution needed  simple and easy to implement No JavaScript  no problems if JS has been disabled No server has to calculate anything for that The user has an immediate feedback Old browser should automatically fallback to input type  text  Mobile browsers can display a specialized keyboard   -Keyboard  Form validation feedback is very easy with CSS3    The apparent downside might be missing validation for old browsers  but that ll change over time  I d prefer this over any of these insane RegEx masterpieces   also see    http   jsfiddle net mYRe7 1  http   diveintohtml5 info forms html http   blog mozilla org webdev 2011 03 14 html5-form-validation-on-sumo

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Nice  I converted the code into java to match the compiler  String pattern       a-zA-Z0-9     amp              -         a-zA-Z0-9     amp              -             x01-  x08  x0b  x0c  x0e-  x1f  x21  x23-  x5b  x5d-  x7f         x01-  x09  x0b  x0c  x0e-  x7f              a-zA-Z0-9     a-zA-Z0-9-   a-zA-Z0-9         a-zA-Z0-9     a-zA-Z0-9-   a-zA-Z0-9              2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9        3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-zA-Z0-9-   a-zA-Z0-9        x01-  x08  x0b  x0c  x0e-  x1f  x21-  x5a  x53-  x7f         x01-  x09  x0b  x0c  x0e-  x7f

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It all depends on how accurate you want to be   For my purposes  where I m just trying to keep out things like bob   aol com  spaces in emails  or steve  no domain at all  or mary aolcom  no period before  com   I use     S   S    S      Sure  it will match things that aren t valid email addresses  but it s a matter of getting common simple errors   There are any number of changes that can be made to that regex  and some are in the comments for this answer   but it s simple  and easy to understand  and is a fine first attempt

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If you want to improve on a regex that has been working reasonably well over several years  then the answer depends on what exactly you want to achieve - what kinds of email addresses have been failing  Fine-tuning email regexes is very difficult  and I have yet to see a perfect solution    If your application involves something very technical in nature  or something internal to organizations   then maybe you need to support IP addresses instead of domain names  or comments in the  local  part of the email address  If your application is multinational  I would consider focusing on Unicode UTF8 support    The leading answer to your question currently links to a  fully RFC-822   compliant regex   However  in spite of the complexity of that regex and its presumed attention to detail in RFC rules  it completely fails when it comes to Unicode support   The regex that I ve written for most of my apps focuses on Unicode support  as well as reasonably good overall adherence to RFC standards                    2   a-zA-Z0-9 u0080- u00FF u0100- u017F u0180- u024F u0250- u02AF u0300- u036F u0370- u03FF u0400- u04FF u0500- u052F u0530- u058F u0590- u05FF u0600- u06FF u0700- u074F u0750- u077F u0780- u07BF u07C0- u07FF u0900- u097F u0980- u09FF u0A00- u0A7F u0A80- u0AFF u0B00- u0B7F u0B80- u0BFF u0C00- u0C7F u0C80- u0CFF u0D00- u0D7F u0D80- u0DFF u0E00- u0E7F u0E80- u0EFF u0F00- u0FFF u1000- u109F u10A0- u10FF u1100- u11FF u1200- u137F u1380- u139F u13A0- u13FF u1400- u167F u1680- u169F u16A0- u16FF u1700- u171F u1720- u173F u1740- u175F u1760- u177F u1780- u17FF u1800- u18AF u1900- u194F u1950- u197F u1980- u19DF u19E0- u19FF u1A00- u1A1F u1B00- u1B7F u1D00- u1D7F u1D80- u1DBF u1DC0- u1DFF u1E00- u1EFF u1F00- u1FFFu20D0- u20FF u2100- u214F u2C00- u2C5F u2C60- u2C7F u2C80- u2CFF u2D00- u2D2F u2D30- u2D7F u2D80- u2DDF u2F00- u2FDF u2FF0- u2FFF u3040- u309F u30A0- u30FF u3100- u312F u3130- u318F u3190- u319F u31C0- u31EF u31F0- u31FF u3200- u32FF u3300- u33FF u3400- u4DBF u4DC0- u4DFF u4E00- u9FFF uA000- uA48F uA490- uA4CF uA700- uA71F uA800- uA82F uA840- uA87F uAC00- uD7AF uF900- uFAFF       amp    -           - d            a-zA-Z0-9 u0080- u00FF u0100- u017F u0180- u024F u0250- u02AF u0300- u036F u0370- u03FF u0400- u04FF u0500- u052F u0530- u058F u0590- u05FF u0600- u06FF u0700- u074F u0750- u077F u0780- u07BF u07C0- u07FF u0900- u097F u0980- u09FF u0A00- u0A7F u0A80- u0AFF u0B00- u0B7F u0B80- u0BFF u0C00- u0C7F u0C80- u0CFF u0D00- u0D7F u0D80- u0DFF u0E00- u0E7F u0E80- u0EFF u0F00- u0FFF u1000- u109F u10A0- u10FF u1100- u11FF u1200- u137F u1380- u139F u13A0- u13FF u1400- u167F u1680- u169F u16A0- u16FF u1700- u171F u1720- u173F u1740- u175F u1760- u177F u1780- u17FF u1800- u18AF u1900- u194F u1950- u197F u1980- u19DF u19E0- u19FF u1A00- u1A1F u1B00- u1B7F u1D00- u1D7F u1D80- u1DBF u1DC0- u1DFF u1E00- u1EFF u1F00- u1FFF u20D0- u20FF u2100- u214F u2C00- u2C5F u2C60- u2C7F u2C80- u2CFF u2D00- u2D2F u2D30- u2D7F u2D80- u2DDF u2F00- u2FDF u2FF0- u2FFF u3040- u309F u30A0- u30FF u3100- u312F u3130- u318F u3190- u319F u31C0- u31EF u31F0- u31FF u3200- u32FF u3300- u33FF u3400- u4DBF u4DC0- u4DFF u4E00- u9FFF uA000- uA48F uA490- uA4CF uA700- uA71F uA800- uA82F uA840- uA87F uAC00- uD7AF uF900- uFAFF -   d         a-zA-Z u0080- u00FF u0100- u017F u0180- u024F u0250- u02AF u0300- u036F u0370- u03FF u0400- u04FF u0500- u052F u0530- u058F u0590- u05FF u0600- u06FF u0700- u074F u0750- u077F u0780- u07BF u07C0- u07FF u0900- u097F u0980- u09FF u0A00- u0A7F u0A80- u0AFF u0B00- u0B7F u0B80- u0BFF u0C00- u0C7F u0C80- u0CFF u0D00- u0D7F u0D80- u0DFF u0E00- u0E7F u0E80- u0EFF u0F00- u0FFF u1000- u109F u10A0- u10FF u1100- u11FF u1200- u137F u1380- u139F u13A0- u13FF u1400- u167F u1680- u169F u16A0- u16FF u1700- u171F u1720- u173F u1740- u175F u1760- u177F u1780- u17FF u1800- u18AF u1900- u194F u1950- u197F u1980- u19DF u19E0- u19FF u1A00- u1A1F u1B00- u1B7F u1D00- u1D7F u1D80- u1DBF u1DC0- u1DFF u1E00- u1EFF u1F00- u1FFF u20D0- u20FF u2100- u214F u2C00- u2C5F u2C60- u2C7F u2C80- u2CFF u2D00- u2D2F u2D30- u2D7F u2D80- u2DDF u2F00- u2FDF u2FF0- u2FFF u3040- u309F u30A0- u30FF u3100- u312F u3130- u318F u3190- u319F u31C0- u31EF u31F0- u31FF u3200- u32FF u3300- u33FF u3400- u4DBF u4DC0- u4DFF u4E00- u9FFF uA000- uA48F uA490- uA4CF uA700- uA71F uA800- uA82F uA840- uA87F uAC00- uD7AF uF900- uFAFF   2 63      i   I ll avoid copy-pasting complete answers  so I ll just link this to a similar answer I provided here  How to validate a unicode email   There is also a live demo available for the regex above at  http   jsfiddle net aossikine qCLVH 3

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As you re writing in PHP I d advice you to use the PHP build-in validation for emails   filter var  value  FILTER VALIDATE EMAIL    If you re running a php-version lower than 5 3 6 please be aware of this issue  https   bugs php net bug php id 53091  If you want more information how this buid-in validation works  see here  Does PHP  39 s filter var FILTER VALIDATE EMAIL actually work

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Don t know about best  but this one is at least correct  as long as the addresses have their comments stripped and replaced with whitespace   Seriously  You should use an already written library for validating emails  The best way is probably to just send a verification e-mail to that address

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If you are fine with accepting empty values  which is not invalid email  and are running PHP 5 2   I would suggest   static public function checkEmail  email   ignore empty   false            if  ignore empty  amp  amp   is null  email      email                         return true          return filter var  email  FILTER VALIDATE EMAIL

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There are plenty examples of this out on the net  and I think even one that fully validates the RFC - but it s tens hundreds of lines long if memory serves   People tend to get carried away validating this sort of thing  Why not just check it has an   and at least one   and meets some simple minimum length  It s trivial to enter a fake email and still match any valid regex anyway  I would guess that false positives are better than false negatives

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There are plenty examples of this out on the net  and I think even one that fully validates the RFC - but it s tens hundreds of lines long if memory serves   People tend to get carried away validating this sort of thing  Why not just check it has an   and at least one   and meets some simple minimum length  It s trivial to enter a fake email and still match any valid regex anyway  I would guess that false positives are better than false negatives

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Had to mention  that nearly has been added new domain  yandex   Possible emails  test job yandex  And also uppercase letters supported  so a bit modified version of acrosman solution is      a-zA-Z0-9-       a-zA-Z0-9-      a-zA-Z0-9-      a-zA-Z0-9-        a-zA-Z  2 6

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this is one of the  regex for email       a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF        a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x22      x20  x09    x0d x0a     x20  x09        x01- x08 x0b x0c x0e- x1f x7f   x21   x23- x5b    x5d- x7e    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF         x01- x09 x0b x0c x0d- x7f    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x20  x09    x0d x0a     x20  x09      x22        a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF           a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF

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As you re writing in PHP I d advice you to use the PHP build-in validation for emails   filter var  value  FILTER VALIDATE EMAIL    If you re running a php-version lower than 5 3 6 please be aware of this issue  https   bugs php net bug php id 53091  If you want more information how this buid-in validation works  see here  Does PHP  39 s filter var FILTER VALIDATE EMAIL actually work

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I use    w   -     w     w   -   w      w   -   w       Which is the one used in ASP NET by the RegularExpressionValidator

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A regex that does exactly what the standards say is allowed  according to what I ve seen about them  is this            -        -        2         254       a-z xC0- xFF0-9     amp                -         253         -     -     a-z0-9-  1 63      a-z  2 63     01   0-9  2  2  0-4  0-9  5 0-5    0-9      3   01   0-9  2  2  0-4  0-9  5 0-5    0-9     gim   Demo   Debuggex analysis  interactive   Split up           -        -        2         254        a-z xC0- xFF0-9     amp                -          253               -     -          a-z0-9-  1 63           a-z  2 63               01   0-9  2  2  0-4  0-9  5 0-5    0-9      3        01   0-9  2  2  0-4  0-9  5 0-5    0-9        Analysis          -        -        2         254        Negative lookahead for either an address starting with a    ending with one  having    in it  or exceeding the 254 character max length      a-z xC0- xFF0-9     amp                -       matching 1 or more of the permitted characters  with the negative look applying to it         253        Negative lookahead for the domain name part  restricting it to 253 characters in total       -     -      Negative lookahead for each of the domain names  which are don t allow starting or ending with        a-z0-9-  1 63        simple group match for the allowed characters in a domain name  which are limited to 63 characters each     a-zA-Z  2 63    simple group match for the allowed top-level domain  which currently still is restricted to letters only  but does include  4 letter TLDs        01   0-9  2  2  0-4  0-9  5 0-5    0-9      3    01   0-9  2  2  0-4  0-9  5 0-5    0-9     the alternative for domain names  this matches the first 3 numbers in an IP address with a   behind it  and then the fourth number in the IP address without   behind it

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UPDATED  I ve collated everything I know about email address validation here  http   isemail info  which now not only validates but also diagnoses problems with email addresses  I agree with many of the comments here that validation is only part of the answer  see my essay at http   isemail info about   is email   remains  as far as I know  the only validator that will tell you definitively whether a given string is a valid email address or not  I ve upload a new version at http   isemail info   I collated test cases from Cal Henderson  Dave Child  Phil Haack  Doug Lovell  RFC5322 and RFC 3696  275 test addresses in all  I ran all these tests against all the free validators I could find   I ll try to keep this page up-to-date as people enhance their validators  Thanks to Cal  Michael  Dave  Paul and Phil for their help and co-operation in compiling these tests and constructive criticism of my own validator   People should be aware of the errata against RFC 3696 in particular  Three of the canonical examples are in fact invalid addresses  And the maximum length of an address is 254 or 256 characters  not 320

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I use    w   -     w     w   -   w      w   -   w       Which is the one used in ASP NET by the RegularExpressionValidator

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While deciding which characters are allowed  please remember your apostrophed and hyphenated friends  I have no control over the fact that my company generates my email address using my name from the HR system  That includes the apostrophe in my last name  I can t tell you how many times I have been blocked from interacting with a website by the fact that my email address is  invalid

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One simple regular expression which would at least not reject any valid email address would be checking for something  followed by an   sign and then something followed by a period and at least 2 somethings  It won t reject anything  but after reviewing the spec I can t find any email that would be valid and rejected   email                    2

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Writing a regular expression for all the things will take a lot of effort  Instead  you can use pyIsEmail package   Below text is taken from pyIsEmail website   pyIsEmail is a no-nonsense approach for checking whether that user-supplied email address could be real   Regular expressions are cheap to write  but often require maintenance when new top-level domains come out or don   t conform to email addressing features that come back into vogue  pyIsEmail allows you to validate an email address     and even check the domain  if you wish     with one simple call  making your code more readable and faster to write  When you want to know why an email address doesn   t validate  they even provide you with a diagnosis   Usage  For the simplest usage  import and use the is email function   from pyisemail import is email  address    test example com  bool result   is email address  detailed result   is email address  diagnose True    You can also check whether the domain used in the email is a valid domain and whether or not it has a valid MX record   from pyisemail import is email  address    test example com  bool result with dns   is email address  check dns True  detailed result with dns   is email address  check dns True  diagnose True    These are primary indicators of whether an email address can even be issued at that domain  However  a valid response here is not a guarantee that the email exists  merely that is can exist   In addition to the base is email functionality  you can also use the validators by themselves  Check the validator source doc to see how this works

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There is not one which is really usable  I discuss some issues in my answer to Is there a php library for email address validation   it is discussed also in Regexp recognition of email address hard   In short  don t expect a single  usable regex to do a proper job  And the best regex will validate the syntax  not the validity of an e-mail  jhohn example com is correct but it will probably bounce

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I know this question is about RegEx  but guessing that 90  of all developers reading these solutions are trying to validate an E-Mail address in an HTML form displayed in a browser    If this is the case  I d suggest checking out the new HTML5  lt input type  email  gt  form element   HTML5     lt input type  email  required   gt    CSS3    input required         background-color  rgba 255 0 0 0 2        input focus invalid         box-shadow  0 0 1em red       border-color  red       input focus valid         box-shadow  0 0 1em green       border-color  green       http   jsfiddle net mYRe7 1  This has a couple of advantages    Automatic validation  no custom solution needed  simple and easy to implement No JavaScript  no problems if JS has been disabled No server has to calculate anything for that The user has an immediate feedback Old browser should automatically fallback to input type  text  Mobile browsers can display a specialized keyboard   -Keyboard  Form validation feedback is very easy with CSS3    The apparent downside might be missing validation for old browsers  but that ll change over time  I d prefer this over any of these insane RegEx masterpieces   also see    http   jsfiddle net mYRe7 1  http   diveintohtml5 info forms html http   blog mozilla org webdev 2011 03 14 html5-form-validation-on-sumo

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UPDATED  I ve collated everything I know about email address validation here  http   isemail info  which now not only validates but also diagnoses problems with email addresses  I agree with many of the comments here that validation is only part of the answer  see my essay at http   isemail info about   is email   remains  as far as I know  the only validator that will tell you definitively whether a given string is a valid email address or not  I ve upload a new version at http   isemail info   I collated test cases from Cal Henderson  Dave Child  Phil Haack  Doug Lovell  RFC5322 and RFC 3696  275 test addresses in all  I ran all these tests against all the free validators I could find   I ll try to keep this page up-to-date as people enhance their validators  Thanks to Cal  Michael  Dave  Paul and Phil for their help and co-operation in compiling these tests and constructive criticism of my own validator   People should be aware of the errata against RFC 3696 in particular  Three of the canonical examples are in fact invalid addresses  And the maximum length of an address is 254 or 256 characters  not 320

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This question is asked a lot  but I think you should step back and ask yourself why you want to validate email adresses syntactically  What is the benefit really    It will not catch common typos  It does not prevent people from entering invalid or made-up email addresses  or entering someone else s address     If you want to validate that an email is correct  you have no choice than to send an confirmation email and have the user reply to that  In many cases you will have to send a confirmation mail anyway for security reasons or for ethical reasons  so you cannot e g  sign someone up to a service against their will

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AS per my understanding most probable will cover by        a-z0-9 -      a-z0-9-       a-z      a-z     a-z      is

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As mentioned already  you can t validate an email with a regex  However  here s what we currently use to make sure user-input isn t totally bogus  forgetting the TLD etc     This regex will allow IDN domains and special characters  like Umlauts  before and after the   sign       w  -          w -      w-  2 63   iu

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You should not use regular expressions to validate email addresses   Instead  use the MailAddress class  like this   try       address   new MailAddress address  Address    catch FormatException           address is invalid     The MailAddress class uses a BNF parser to validate the address in full accordance with RFC822   If you plan to use the MailAddress to validate the e-mail address  be aware that this approach accepts the display name part of the e-mail address as well  and that may not be exactly what you want to achieve  For example  it accepts these strings as valid e-mail addresses     user1 hotmail com  user2 gmail com   user1 hotmail com  user2 gmail com  user3 company com   User Display Name user3 company com   user4  company com    In some of these cases  only the last part of the strings is parsed as the address  the rest before that is the display name  To get a plain e-mail address without any display name  you can check the normalized address against your original string   bool isValid   false   try       MailAddress address   new MailAddress emailAddress       isValid    address Address    emailAddress          or        isValid   string IsNullOrEmpty address DisplayName     catch  FormatException           address is invalid     Furthermore  an address having a dot at the end  like user company  is accepted by MailAddress as well   If you really want to use a regex  here it is                  r n     t                 lt  gt               000- 031            r n     t      Z           lt  gt                          r               r n     t             r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n      t            r n     t              r n     t           lt  gt               000- 0 31            r n     t     Z           lt  gt                           r                   r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t               lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n      t       lt        r n     t               lt  gt               000- 031             r n     t     Z           lt  gt                           r                  r n      t                r n     t           lt  gt               000- 031            r n      t     Z           lt  gt                           r                  r n     t                   r n     t           lt  gt               000- 031            r n      t     Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t             lt  gt               000- 031            r n     t      Z           lt  gt                          r               r n     t            r  n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n     t             r n     t              r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t        gt        r n     t             lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n      t            r n     t             r n     t                 lt  gt                000- 031            r n     t     Z           lt  gt                          r                r n     t            r n     t                r n     t           lt  gt                 000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t              r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t               lt  gt               000-  031            r n     t     Z           lt  gt                          r                r n     t            r n     t       lt        r n     t               lt  gt                000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                            r                  r n     t                  r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                           r                   r n     t                r n     t             lt  gt               0 00- 031            r n     t     Z           lt  gt                          r                r n     t            r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t              r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t        gt        r n     t         s             lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n     t               r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t       lt        r n      t               lt  gt               000- 031            r n     t     Z            lt  gt                           r                  r n     t                r n      t           lt  gt               000- 031            r n     t     Z           lt  gt                             r                  r n     t                  r n      t           lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t              lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n     t               r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                           r                  r n     t        gt         r n     t          s

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Here s the PHP I use  I ve choosen this solution in the spirit of  false positives are better than false negatives  as declared by another commenter here AND with regards to keeping your response time up and server load down     there s really no need to waste server resources with a regular expression when this will weed out most simple user error  You can always follow this up by sending a test email if you want   function validateEmail  email      return  bool  stripos  email

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No one mentioned the issue of localization  i18   what if you have clients coming from all over the world  You will need to then need to sub-categorize your regex per country area  which I have seen developers ending up building a large dictionary config  Detecting users  browser language setting may be a good starting point

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Strange that you  cannot  allow 4 characters TLDs   You are banning people from  info and  name  and the length limitation stop  travel and  museum  but yes  they are less common than 2 characters TLDs and 3 characters TLDs   You should allow uppercase alphabets too   Email systems will normalize the local part and domain part   For your regex of domain part  domain name cannot starts with  -  and cannot ends with  -   Dash can only stays in between   If you used the PEAR library  check out their mail function  forgot the exact name library    You can validate email address by calling one function  and it validates the email address according to definition in RFC822

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The regular expressions posted in this thread are out of date now because of the new generic top level domains  gTLDs  coming in  e g   london   basketball        To validate an email address there are two answers  That would be relevant to the vast majority     As the main answer says - don t use a regular expression  just validate it by sending an email to the address  Catch exceptions for invalid addresses  Use a very generic regex to at least make sure that they are using an email structure  something   something   something   There s no point in going for a detailed regex because you won t catch them all and there ll be a new batch in a few years and you ll have to update your regular expression again    I have decided to use the regular expression because  unfortunately  some users don t read forms and put the wrong data in the wrong fields  This will at least alert them when they try to put something which isn t an email into the email input field and should save you some time supporting users on email issues             2         2

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Cal Henderson  Flickr  wrote an article called Parsing Email Adresses in PHP and shows how to do proper RFC  2 822-compliant Email Address parsing   You can also get the source code in php  python and ruby which is cc licensed

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It depends on what you mean by best  If you re talking about catching every valid email address use the following          r n     t                 lt  gt               000- 031            r n     t      Z           lt  gt                          r               r n     t             r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n      t            r n     t              r n     t           lt  gt               000- 0 31            r n     t     Z           lt  gt                           r                   r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t               lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n      t       lt        r n     t               lt  gt               000- 031             r n     t     Z           lt  gt                           r                  r n      t                r n     t           lt  gt               000- 031            r n      t     Z           lt  gt                           r                  r n     t                   r n     t           lt  gt               000- 031            r n      t     Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t             lt  gt               000- 031            r n     t      Z           lt  gt                          r               r n     t            r  n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n     t             r n     t              r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t        gt        r n     t             lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n      t            r n     t             r n     t                 lt  gt                000- 031            r n     t     Z           lt  gt                          r                r n     t            r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t              r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t               lt  gt               000-  031            r n     t     Z           lt  gt                          r                r n     t            r n     t       lt        r n     t               lt  gt                000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                            r                  r n     t                  r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                           r                   r n     t                r n     t             lt  gt               0 00- 031            r n     t     Z           lt  gt                          r                r n     t            r n     t                r n     t           lt  gt                000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t              r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t        gt        r n     t         s             lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n     t               r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t       lt        r n      t               lt  gt               000- 031            r n     t     Z            lt  gt                           r                  r n     t                r n      t           lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                  r n      t           lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t              lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n     t               r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                           r                  r n     t        gt         r n     t          s      http   www ex-parrot com  pdw Mail-RFC822-Address html  If you re looking for something simpler but that will catch most valid email addresses try something like       a-zA-Z0-9   -    a-zA-Z0-9-     a-zA-Z0-9-        EDIT  From the link      This regular expression will only validate addresses that have had any comments stripped and replaced with whitespace  this is done by the module

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Cal Henderson  Flickr  wrote an article called Parsing Email Adresses in PHP and shows how to do proper RFC  2 822-compliant Email Address parsing   You can also get the source code in php  python and ruby which is cc licensed

User · Answer

I m still using     A-Za-z0-9    -      A-Za-z0-9  -     A-Za-z  2      But with IPv6 and Unicode coming up  perhaps     w    s       s  2      is best  Gmail already allows sequential dots  but Microsoft Exchange Server 2007 refuses them

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Strange that you  cannot  allow 4 characters TLDs   You are banning people from  info and  name  and the length limitation stop  travel and  museum  but yes  they are less common than 2 characters TLDs and 3 characters TLDs   You should allow uppercase alphabets too   Email systems will normalize the local part and domain part   For your regex of domain part  domain name cannot starts with  -  and cannot ends with  -   Dash can only stays in between   If you used the PEAR library  check out their mail function  forgot the exact name library    You can validate email address by calling one function  and it validates the email address according to definition in RFC822

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Per the W3C HTML5 spec     a-zA-Z0-9      amp              -    a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9         a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9         Context      A valid e-mail address is a string that matches the ABNF production             Note  This requirement is a willful violation of RFC 5322  which defines a syntax for e-mail addresses that is simultaneously too strict  before the         character   too vague  after the         character   and too lax  allowing comments  whitespace characters  and quoted strings in manners unfamiliar to most users  to be of practical use here       The following JavaScript- and Perl-compatible regular expression is an implementation of the above definition          a-zA-Z0-9      amp              -    a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9         a-zA-Z0-9     a-zA-Z0-9-  0 61  a-zA-Z0-9

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There are now many more  1000s  of TLD s  Most of the answers in here need to be voted down as they are no longer correct - potentially this question should have a 2nd edition   Feel free to visit a more current discussion on other post

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I did not find any that deals with top level domain name but it should be considered   So for me following worked-   a-z0-9     amp              -        a-z0-9     amp              -         a-z0-9     a-z0-9-   a-z0-9           A-Z  2 AAA AARP ABB ABBOTT ABOGADO AC ACADEMY ACCENTURE ACCOUNTANT ACCOUNTANTS ACO ACTIVE ACTOR AD ADAC ADS ADULT AE AEG AERO AF AFL AG AGENCY AI AIG AIRFORCE AIRTEL AL ALIBABA ALIPAY ALLFINANZ ALSACE AM AMICA AMSTERDAM ANALYTICS ANDROID AO APARTMENTS APP APPLE AQ AQUARELLE AR ARAMCO ARCHI ARMY ARPA ARTE AS ASIA ASSOCIATES AT ATTORNEY AU AUCTION AUDI AUDIO AUTHOR AUTO AUTOS AW AX AXA AZ AZURE BA BAIDU BAND BANK BAR BARCELONA BARCLAYCARD BARCLAYS BARGAINS BAUHAUS BAYERN BB BBC BBVA BCN BD BE BEATS BEER BENTLEY BERLIN BEST BET BF BG BH BHARTI BI BIBLE BID BIKE BING BINGO BIO BIZ BJ BLACK BLACKFRIDAY BLOOMBERG BLUE BM BMS BMW BN BNL BNPPARIBAS BO BOATS BOEHRINGER BOM BOND BOO BOOK BOOTS BOSCH BOSTIK BOT BOUTIQUE BR BRADESCO BRIDGESTONE BROADWAY BROKER BROTHER BRUSSELS BS BT BUDAPEST BUGATTI BUILD BUILDERS BUSINESS BUY BUZZ BV BW BY BZ BZH CA CAB CAFE CAL CALL CAMERA CAMP CANCERRESEARCH CANON CAPETOWN CAPITAL CAR CARAVAN CARDS CARE CAREER CAREERS CARS CARTIER CASA CASH CASINO CAT CATERING CBA CBN CC CD CEB CENTER CEO CERN CF CFA CFD CG CH CHANEL CHANNEL CHAT CHEAP CHLOE CHRISTMAS CHROME CHURCH CI CIPRIANI CIRCLE CISCO CITIC CITY CITYEATS CK CL CLAIMS CLEANING CLICK CLINIC CLINIQUE CLOTHING CLOUD CLUB CLUBMED CM CN CO COACH CODES COFFEE COLLEGE COLOGNE COM COMMBANK COMMUNITY COMPANY COMPARE COMPUTER COMSEC CONDOS CONSTRUCTION CONSULTING CONTACT CONTRACTORS COOKING COOL COOP CORSICA COUNTRY COUPONS COURSES CR CREDIT CREDITCARD CREDITUNION CRICKET CROWN CRS CRUISES CSC CU CUISINELLA CV CW CX CY CYMRU CYOU CZ DABUR DAD DANCE DATE DATING DATSUN DAY DCLK DE DEALER DEALS DEGREE DELIVERY DELL DELTA DEMOCRAT DENTAL DENTIST DESI DESIGN DEV DIAMONDS DIET DIGITAL DIRECT DIRECTORY DISCOUNT DJ DK DM DNP DO DOCS DOG DOHA DOMAINS DOOSAN DOWNLOAD DRIVE DUBAI DURBAN DVAG DZ EARTH EAT EC EDEKA EDU EDUCATION EE EG EMAIL EMERCK ENERGY ENGINEER ENGINEERING ENTERPRISES EPSON EQUIPMENT ER ERNI ES ESQ ESTATE ET EU EUROVISION EUS EVENTS EVERBANK EXCHANGE EXPERT EXPOSED EXPRESS FAGE FAIL FAIRWINDS FAITH FAMILY FAN FANS FARM FASHION FAST FEEDBACK FERRERO FI FILM FINAL FINANCE FINANCIAL FIRESTONE FIRMDALE FISH FISHING FIT FITNESS FJ FK FLIGHTS FLORIST FLOWERS FLSMIDTH FLY FM FO FOO FOOTBALL FORD FOREX FORSALE FORUM FOUNDATION FOX FR FRESENIUS FRL FROGANS FUND FURNITURE FUTBOL FYI GA GAL GALLERY GAME GARDEN GB GBIZ GD GDN GE GEA GENT GENTING GF GG GGEE GH GI GIFT GIFTS GIVES GIVING GL GLASS GLE GLOBAL GLOBO GM GMAIL GMO GMX GN GOLD GOLDPOINT GOLF GOO GOOG GOOGLE GOP GOT GOV GP GQ GR GRAINGER GRAPHICS GRATIS GREEN GRIPE GROUP GS GT GU GUCCI GUGE GUIDE GUITARS GURU GW GY HAMBURG HANGOUT HAUS HEALTH HEALTHCARE HELP HELSINKI HERE HERMES HIPHOP HITACHI HIV HK HM HN HOCKEY HOLDINGS HOLIDAY HOMEDEPOT HOMES HONDA HORSE HOST HOSTING HOTELES HOTMAIL HOUSE HOW HR HSBC HT HU HYUNDAI IBM ICBC ICE ICU ID IE IFM IINET IL IM IMMO IMMOBILIEN IN INDUSTRIES INFINITI INFO ING INK INSTITUTE INSURANCE INSURE INT INTERNATIONAL INVESTMENTS IO IPIRANGA IQ IR IRISH IS ISELECT IST ISTANBUL IT ITAU IWC JAGUAR JAVA JCB JE JETZT JEWELRY JLC JLL JM JMP JO JOBS JOBURG JOT JOY JP JPRS JUEGOS KAUFEN KDDI KE KFH KG KH KI KIA KIM KINDER KITCHEN KIWI KM KN KOELN KOMATSU KP KPN KR KRD KRED KW KY KYOTO KZ LA LACAIXA LAMBORGHINI LAMER LANCASTER LAND LANDROVER LANXESS LASALLE LAT LATROBE LAW LAWYER LB LC LDS LEASE LECLERC LEGAL LEXUS LGBT LI LIAISON LIDL LIFE LIFEINSURANCE LIFESTYLE LIGHTING LIKE LIMITED LIMO LINCOLN LINDE LINK LIVE LIVING LIXIL LK LOAN LOANS LOL LONDON LOTTE LOTTO LOVE LR LS LT LTD LTDA LU LUPIN LUXE LUXURY LV LY MA MADRID MAIF MAISON MAKEUP MAN MANAGEMENT MANGO MARKET MARKETING MARKETS MARRIOTT MBA MC MD ME MED MEDIA MEET MELBOURNE MEME MEMORIAL MEN MENU MEO MG MH MIAMI MICROSOFT MIL MINI MK ML MM MMA MN MO MOBI MOBILY MODA MOE MOI MOM MONASH MONEY MONTBLANC MORMON MORTGAGE MOSCOW MOTORCYCLES MOV MOVIE MOVISTAR MP MQ MR MS MT MTN MTPC MTR MU MUSEUM MUTUELLE MV MW MX MY MZ NA NADEX NAGOYA NAME NAVY NC NE NEC NET NETBANK NETWORK NEUSTAR NEW NEWS NEXUS NF NG NGO NHK NI NICO NINJA NISSAN NL NO NOKIA NORTON NOWRUZ NP NR NRA NRW NTT NU NYC NZ OBI OFFICE OKINAWA OM OMEGA ONE ONG ONL ONLINE OOO ORACLE ORANGE ORG ORGANIC ORIGINS OSAKA OTSUKA OVH PA PAGE PAMPEREDCHEF PANERAI PARIS PARS PARTNERS PARTS PARTY PE PET PF PG PH PHARMACY PHILIPS PHOTO PHOTOGRAPHY PHOTOS PHYSIO PIAGET PICS PICTET PICTURES PID PIN PING PINK PIZZA PK PL PLACE PLAY PLAYSTATION PLUMBING PLUS PM PN POHL POKER PORN POST PR PRAXI PRESS PRO PROD PRODUCTIONS PROF PROMO PROPERTIES PROPERTY PROTECTION PS PT PUB PW PY QA QPON QUEBEC RACING RE READ REALTOR REALTY RECIPES RED REDSTONE REDUMBRELLA REHAB REISE REISEN REIT REN RENT RENTALS REPAIR REPORT REPUBLICAN REST RESTAURANT REVIEW REVIEWS REXROTH RICH RICOH RIO RIP RO ROCHER ROCKS RODEO ROOM RS RSVP RU RUHR RUN RW RWE RYUKYU SA SAARLAND SAFE SAFETY SAKURA SALE SALON SAMSUNG SANDVIK SANDVIKCOROMANT SANOFI SAP SAPO SARL SAS SAXO SB SBS SC SCA SCB SCHAEFFLER SCHMIDT SCHOLARSHIPS SCHOOL SCHULE SCHWARZ SCIENCE SCOR SCOT SD SE SEAT SECURITY SEEK SELECT SENER SERVICES SEVEN SEW SEX SEXY SFR SG SH SHARP SHELL SHIA SHIKSHA SHOES SHOW SHRIRAM SI SINGLES SITE SJ SK SKI SKIN SKY SKYPE SL SM SMILE SN SNCF SO SOCCER SOCIAL SOFTBANK SOFTWARE SOHU SOLAR SOLUTIONS SONY SOY SPACE SPIEGEL SPREADBETTING SR SRL ST STADA STAR STARHUB STATEFARM STATOIL STC STCGROUP STOCKHOLM STORAGE STUDIO STUDY STYLE SU SUCKS SUPPLIES SUPPLY SUPPORT SURF SURGERY SUZUKI SV SWATCH SWISS SX SY SYDNEY SYMANTEC SYSTEMS SZ TAB TAIPEI TAOBAO TATAMOTORS TATAR TATTOO TAX TAXI TC TCI TD TEAM TECH TECHNOLOGY TEL TELEFONICA TEMASEK TENNIS TF TG TH THD THEATER THEATRE TICKETS TIENDA TIFFANY TIPS TIRES TIROL TJ TK TL TM TMALL TN TO TODAY TOKYO TOOLS TOP TORAY TOSHIBA TOURS TOWN TOYOTA TOYS TR TRADE TRADING TRAINING TRAVEL TRAVELERS TRAVELERSINSURANCE TRUST TRV TT TUBE TUI TUSHU TV TW TZ UA UBS UG UK UNIVERSITY UNO UOL US UY UZ VA VACATIONS VANA VC VE VEGAS VENTURES VERISIGN VERSICHERUNG VET VG VI VIAJES VIDEO VILLAS VIN VIP VIRGIN VISION VISTA VISTAPRINT VIVA VLAANDEREN VN VODKA VOLKSWAGEN VOTE VOTING VOTO VOYAGE VU WALES WALTER WANG WANGGOU WATCH WATCHES WEATHER WEBCAM WEBER WEBSITE WED WEDDING WEIR WF WHOSWHO WIEN WIKI WILLIAMHILL WIN WINDOWS WINE WME WORK WORKS WORLD WS WTC WTF XBOX XEROX XIN XN--11B4C3D XN--1QQW23A XN--30RR7Y XN--3BST00M XN--3DS443G XN--3E0B707E XN--3PXU8K XN--42C2D9A XN--45BRJ9C XN--45Q11C XN--4GBRIM XN--55QW42G XN--55QX5D XN--6FRZ82G XN--6QQ986B3XL XN--80ADXHKS XN--80AO21A XN--80ASEHDB XN--80ASWG XN--90A3AC XN--90AIS XN--9DBQ2A XN--9ET52U XN--B4W605FERD XN--C1AVG XN--C2BR7G XN--CG4BKI XN--CLCHC0EA0B2G2A9GCD XN--CZR694B XN--CZRS0T XN--CZRU2D XN--D1ACJ3B XN--D1ALF XN--ECKVDTC9D XN--EFVY88H XN--ESTV75G XN--FHBEI XN--FIQ228C5HS XN--FIQ64B XN--FIQS8S XN--FIQZ9S XN--FJQ720A XN--FLW351E XN--FPCRJ9C3D XN--FZC2C9E2C XN--G2XX48C XN--GECRJ9C XN--H2BRJ9C XN--HXT814E XN--I1B6B1A6A2E XN--IMR513N XN--IO0A7I XN--J1AEF XN--J1AMH XN--J6W193G XN--JLQ61U9W7B XN--KCRX77D1X4A XN--KPRW13D XN--KPRY57D XN--KPU716F XN--KPUT3I XN--L1ACC XN--LGBBAT1AD8J XN--MGB9AWBF XN--MGBA3A3EJT XN--MGBA3A4F16A XN--MGBAAM7A8H XN--MGBAB2BD XN--MGBAYH7GPA XN--MGBB9FBPOB XN--MGBBH1A71E XN--MGBC0A9AZCG XN--MGBERP4A5D4AR XN--MGBPL2FH XN--MGBT3DHD XN--MGBTX2B XN--MGBX4CD0AB XN--MK1BU44C XN--MXTQ1M XN--NGBC5AZD XN--NGBE9E0A XN--NODE XN--NQV7F XN--NQV7FS00EMA XN--NYQY26A XN--O3CW4H XN--OGBPF8FL XN--P1ACF XN--P1AI XN--PBT977C XN--PGBS0DH XN--PSSY2U XN--Q9JYB4C XN--QCKA1PMC XN--QXAM XN--RHQV96G XN--S9BRJ9C XN--SES554G XN--T60B56A XN--TCKWE XN--UNUP4Y XN--VERMGENSBERATER-CTB XN--VERMGENSBERATUNG-PWB XN--VHQUV XN--VUQ861B XN--WGBH1C XN--WGBL6A XN--XHQ521B XN--XKC2AL3HYE2A XN--XKC2DL3A5EE0H XN--Y9A3AQ XN--YFRO4I67O XN--YGBI2AMMX XN--ZFR164B XPERIA XXX XYZ YACHTS YAMAXUN YANDEX YE YODOBASHI YOGA YOKOHAMA YOUTUBE YT ZA ZARA ZERO ZIP ZM ZONE ZUERICH ZW  b   That easily discarded emails like 3c296rD3HNEE d139c a51  Sd sd dox etc  Domain name can be further edited if needed e g  specific country domain etc

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I use multi-step validation  As there is no perfect way to validate email address  perfect one can t be made  but at least you can notify user he she is doing something wrong - here is my approach  1  I first validate with the very basic regex which just checks if email contains exactly one   sign and it is not blank before or after that sign  e g        s       s      2a  if the first validator does not pass  and for most addresses it should although it is not perfect   then warn the user the email is invalid and do not allow him her to continue with the input  2b  if it passes  then validate against more strict regex - something which might disallow valid emails  If it does not pass  user is warned about possible error but allowed to continue  Unlike the step  1  where the user is not allowed to continue because it is an obvious error   So in other words  the first liberal validation is just to strip obvious errors and it is treated as  error   People type a blank address  address without   sign and so on  This should be treated as error  The second one is more strict but treated as  warning  and user is allowed to continue with the input but warned to at least examine if he she entered a valid entry  The key here is in error warning approach - error being something which can t under 99 99  circumstances be valid email   Of couse  you can adjust what makes a first regex more liberal and second one more strict   Depending on what you need  the above approach might work for you

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It   s easy in Perl 5 10 or newer       DEFINE        lt address gt             amp mailbox       amp group         lt mailbox gt             amp name addr       amp addr spec         lt name addr gt           amp display name      amp angle addr         lt angle addr gt          amp CFWS    lt     amp addr spec   gt     amp CFWS          lt group gt               amp display name          amp mailbox list       amp CFWS                                                   amp CFWS          lt display name gt        amp phrase         lt mailbox list gt        amp mailbox           amp mailbox            lt addr spec gt           amp local part        amp domain         lt local part gt          amp dot atom       amp quoted string         lt domain gt              amp dot atom       amp domain literal         lt domain literal gt      amp CFWS             amp FWS      amp dcontent       amp FWS                                          amp CFWS          lt dcontent gt            amp dtext       amp quoted pair         lt dtext gt               amp NO WS CTL      x21- x5a x5e- x7e          lt atext gt               amp ALPHA       amp DIGIT           amp    -                   lt atom gt                amp CFWS      amp atext      amp CFWS          lt dot atom gt            amp CFWS      amp dot atom text     amp CFWS          lt dot atom text gt       amp atext             amp atext             lt text gt               x01- x09 x0b x0c x0e- x7f         lt quoted pair gt            amp text          lt qtext gt               amp NO WS CTL      x21 x23- x5b x5d- x7e         lt qcontent gt            amp qtext       amp quoted pair         lt quoted string gt       amp CFWS      amp DQUOTE        amp FWS      amp qcontent                               amp FWS      amp DQUOTE     amp CFWS           lt word gt                amp atom       amp quoted string         lt phrase gt              amp word          Folding white space       lt FWS gt                     amp WSP      amp CRLF       amp WSP          lt ctext gt               amp NO WS CTL      x21- x27 x2a- x5b x5d- x7e         lt ccontent gt            amp ctext       amp quoted pair       amp comment         lt comment gt                    amp FWS      amp ccontent       amp FWS              lt CFWS gt                    amp FWS      amp comment                                     amp FWS      amp comment        amp FWS          No whitespace control       lt NO WS CTL gt          x01- x08 x0b x0c x0e- x1f x7f          lt ALPHA gt             A-Za-z         lt DIGIT gt             0-9         lt CRLF gt              x0d  x0a        lt DQUOTE gt                    lt WSP gt                x20 x09           amp address  x

User · Answer

The fully RFC 822 compliant regex is inefficient and obscure because of its length   Fortunately  RFC 822 was superseded twice and the current specification for email addresses is RFC 5322   RFC 5322 leads to a regex that can be understood if studied for a few minutes and is efficient enough for actual use   One RFC 5322 compliant regex can be found at the top of the page at http   emailregex com  but uses the IP address pattern that is floating around the internet with a bug that allows 00 for any of the unsigned byte decimal values in a dot-delimited address  which is illegal   The rest of it appears to be consistent with the RFC 5322 grammar and passes several tests using grep -Po  including cases domain names  IP addresses  bad ones  and account names with and without quotes   Correcting the 00 bug in the IP pattern  we obtain a working and fairly fast regex    Scrape the rendered version  not the markdown  for actual code           a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9             2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9       3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          or       a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9             2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9       3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          Here is diagram of finite state machine for above regexp which is more clear than regexp itself   The more sophisticated patterns in Perl and PCRE  regex library used e g  in PHP  can correctly parse RFC 5322 without a hitch  Python and C  can do that too  but they use a different syntax from those first two  However  if you are forced to use one of the many less powerful pattern-matching languages  then it   s best to use a real parser   It s also important to understand that validating it per the RFC tells you absolutely nothing about whether that address actually exists at the supplied domain  or whether the person entering the address is its true owner  People sign others up to mailing lists this way all the time  Fixing that requires a fancier kind of validation that involves sending that address a message that includes a confirmation token meant to be entered on the same web page as was the address    Confirmation tokens are the only way to know you got the address of the person entering it  This is why most mailing lists now use that mechanism to confirm sign-ups  After all  anybody can put down president whitehouse gov  and that will even parse as legal  but it isn t likely to be the person at the other end   For PHP  you should not use the pattern given in Validate an E-Mail Address with PHP  the Right Way from which I quote      There is some danger that common usage and widespread sloppy coding will establish a de facto standard for e-mail addresses that is more restrictive than the recorded formal standard    That is no better than all the other non-RFC patterns  It isn   t even smart enough to handle even RFC 822  let alone RFC 5322  This one  however  is   If you want to get fancy and pedantic  implement a complete state engine  A regular expression can only act as a rudimentary filter  The problem with regular expressions is that telling someone that their perfectly valid e-mail address is invalid  a false positive  because your regular expression can t handle it is just rude and impolite from the user s perspective  A state engine for the purpose can both validate and even correct e-mail addresses that would otherwise be considered invalid as it disassembles the e-mail address according to each RFC  This allows for a potentially more pleasing experience  like     The specified e-mail address  myemail address com  is invalid  Did you mean  myemail address com     See also Validating Email Addresses  including the comments  Or Comparing E-mail Address Validating Regular Expressions     Debuggex Demo

User · Answer

In order to validate an email address with JavaScript it is more convenient and efficient use this function  according with w3school    function validateEmail     var x document f email value  var atpos x indexOf       var dotpos x lastIndexOf       if  atpos lt 1    dotpos lt atpos 2    dotpos 2 gt  x length          alert  Not a valid e-mail address       return false           I use it and it s perfect  I hope to be useful

User · Answer

Not to mention that non-Latin  Chinese  Arabic  Greek  Hebrew  Cyrillic and so on  domain names are to be allowed in the near future  Everyone has to change the email regex used  because those characters are surely not to be covered by  a-z  i nor  w  They will all fail   After all  the best way to validate the email address is still to actually send an email to the address in question to validate the address  If the email address is part of user authentication  register login etc   then you can perfectly combine it with the user activation system  I e  send an email with a link with an unique activation key to the specified email address and only allow login when the user has activated the newly created account using the link in the email   If the purpose of the regex is just to quickly inform the user in the UI that the specified email address doesn t look like in the right format  best is still to check if it matches basically the following regex                                               Simple as that  Why on earth would you care about the characters used in the name and domain  It s the client s responsibility to enter a valid email address  not the server s  Even when the client enters a syntactically valid email address like aa bb cc  this does not guarantee that it s a legit email address  No one regex can cover that

User · Answer

I always use the below regular expression to validate the email address. This is the best regex I have ever seen to validate email address.

"\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\Z";

This regular expression I always uses in my Asp.NET Code and I'm pretty satisfied with it.

use this assembly reference

using System.Text.RegularExpressions;

and try the following code, as it is simple and do the work for you.

private bool IsValidEmail(string email) {
    bool isValid = false;
    const string pattern = @"\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\Z";

    isValid = email != "" && Regex.IsMatch(email, pattern);

    // an alternative of the above line is also given and commented
    //
    //if (email == "") {
    //    isValid = false;
    //} else {
    //    // address provided so use the IsMatch Method
    //    // of the Regular Expression object
    //    isValid = Regex.IsMatch(email, pattern);
    //}
    return isValid;
}

this function validates the email string. If the email string is null, it returns false, if the email string is not in a correct format it returns false. It only returns true if the format of the email is valid.

User · Answer

I never bother creating with my own regular expression  because chances are that someone else has already come up with a better version   I always use regexlib to find one to my liking

User · Answer

Following is the regular expression for validating email address       w     w

User · Answer

I found a regular expression that is compliant to RFC 2822  The preceding standard to  RFC 5322  This regular expression appears to perform fairly well and will cover most cases  however with RFC 5322 becoming the standard there may be some holes that ought to be plugged        a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9            25 0-5  2 0-4  0-9   01   0-9  0-9       3    25 0-5  2 0-4  0-9   01   0-9  0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f           The documentation says you shouldn t use the above regular expression  but instead favour this flavour  which is a bit more manageable    a-z0-9     amp              -        a-z0-9     amp              -         a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9      I noticed this is case-sensitive  so I actually made an alteration to this landing     a-zA-Z0-9     amp              -        a-zA-Z0-9     amp              -         a-zA-Z0-9     a-zA-Z0-9-   a-zA-Z0-9        a-zA-Z0-9     a-zA-Z0-9-   a-zA-Z0-9

User · Answer

Just about every RegEx I ve seen - including some used by Microsoft will not allow the following valid email to get through   simon- hotmail com  Just had a real customer with an email address in this format who couldn t place an order   Here s what I settled on     A minimal Regex that won t have false negatives  Alternatively use the MailAddress constructor with some additional checks  see below   Checking for common typos  cmo or  gmial com and asking for confirmation Are you sure this is your correct email address  It looks like there may be a mistake  Allow the user to accept what they typed if they are sure  Handling bounces when the email is actually sent and manually verifying them to check for obvious mistakes              try                       var email   new MailAddress str                if  email Host EndsWith   cmo                                  return EmailValidation PossibleTypo                             if   email Host EndsWith       amp  amp  email Host Contains                                     return EmailValidation OK                                  catch                       return EmailValidation Invalid

User · Answer

Cal Henderson  Flickr  wrote an article called Parsing Email Adresses in PHP and shows how to do proper RFC  2 822-compliant Email Address parsing   You can also get the source code in php  python and ruby which is cc licensed

User · Answer

Not to mention that non-Latin  Chinese  Arabic  Greek  Hebrew  Cyrillic and so on  domain names are to be allowed in the near future  Everyone has to change the email regex used  because those characters are surely not to be covered by  a-z  i nor  w  They will all fail   After all  the best way to validate the email address is still to actually send an email to the address in question to validate the address  If the email address is part of user authentication  register login etc   then you can perfectly combine it with the user activation system  I e  send an email with a link with an unique activation key to the specified email address and only allow login when the user has activated the newly created account using the link in the email   If the purpose of the regex is just to quickly inform the user in the UI that the specified email address doesn t look like in the right format  best is still to check if it matches basically the following regex                                               Simple as that  Why on earth would you care about the characters used in the name and domain  It s the client s responsibility to enter a valid email address  not the server s  Even when the client enters a syntactically valid email address like aa bb cc  this does not guarantee that it s a legit email address  No one regex can cover that

User · Answer

I did not find any that deals with top level domain name but it should be considered   So for me following worked-   a-z0-9     amp              -        a-z0-9     amp              -         a-z0-9     a-z0-9-   a-z0-9           A-Z  2 AAA AARP ABB ABBOTT ABOGADO AC ACADEMY ACCENTURE ACCOUNTANT ACCOUNTANTS ACO ACTIVE ACTOR AD ADAC ADS ADULT AE AEG AERO AF AFL AG AGENCY AI AIG AIRFORCE AIRTEL AL ALIBABA ALIPAY ALLFINANZ ALSACE AM AMICA AMSTERDAM ANALYTICS ANDROID AO APARTMENTS APP APPLE AQ AQUARELLE AR ARAMCO ARCHI ARMY ARPA ARTE AS ASIA ASSOCIATES AT ATTORNEY AU AUCTION AUDI AUDIO AUTHOR AUTO AUTOS AW AX AXA AZ AZURE BA BAIDU BAND BANK BAR BARCELONA BARCLAYCARD BARCLAYS BARGAINS BAUHAUS BAYERN BB BBC BBVA BCN BD BE BEATS BEER BENTLEY BERLIN BEST BET BF BG BH BHARTI BI BIBLE BID BIKE BING BINGO BIO BIZ BJ BLACK BLACKFRIDAY BLOOMBERG BLUE BM BMS BMW BN BNL BNPPARIBAS BO BOATS BOEHRINGER BOM BOND BOO BOOK BOOTS BOSCH BOSTIK BOT BOUTIQUE BR BRADESCO BRIDGESTONE BROADWAY BROKER BROTHER BRUSSELS BS BT BUDAPEST BUGATTI BUILD BUILDERS BUSINESS BUY BUZZ BV BW BY BZ BZH CA CAB CAFE CAL CALL CAMERA CAMP CANCERRESEARCH CANON CAPETOWN CAPITAL CAR CARAVAN CARDS CARE CAREER CAREERS CARS CARTIER CASA CASH CASINO CAT CATERING CBA CBN CC CD CEB CENTER CEO CERN CF CFA CFD CG CH CHANEL CHANNEL CHAT CHEAP CHLOE CHRISTMAS CHROME CHURCH CI CIPRIANI CIRCLE CISCO CITIC CITY CITYEATS CK CL CLAIMS CLEANING CLICK CLINIC CLINIQUE CLOTHING CLOUD CLUB CLUBMED CM CN CO COACH CODES COFFEE COLLEGE COLOGNE COM COMMBANK COMMUNITY COMPANY COMPARE COMPUTER COMSEC CONDOS CONSTRUCTION CONSULTING CONTACT CONTRACTORS COOKING COOL COOP CORSICA COUNTRY COUPONS COURSES CR CREDIT CREDITCARD CREDITUNION CRICKET CROWN CRS CRUISES CSC CU CUISINELLA CV CW CX CY CYMRU CYOU CZ DABUR DAD DANCE DATE DATING DATSUN DAY DCLK DE DEALER DEALS DEGREE DELIVERY DELL DELTA DEMOCRAT DENTAL DENTIST DESI DESIGN DEV DIAMONDS DIET DIGITAL DIRECT DIRECTORY DISCOUNT DJ DK DM DNP DO DOCS DOG DOHA DOMAINS DOOSAN DOWNLOAD DRIVE DUBAI DURBAN DVAG DZ EARTH EAT EC EDEKA EDU EDUCATION EE EG EMAIL EMERCK ENERGY ENGINEER ENGINEERING ENTERPRISES EPSON EQUIPMENT ER ERNI ES ESQ ESTATE ET EU EUROVISION EUS EVENTS EVERBANK EXCHANGE EXPERT EXPOSED EXPRESS FAGE FAIL FAIRWINDS FAITH FAMILY FAN FANS FARM FASHION FAST FEEDBACK FERRERO FI FILM FINAL FINANCE FINANCIAL FIRESTONE FIRMDALE FISH FISHING FIT FITNESS FJ FK FLIGHTS FLORIST FLOWERS FLSMIDTH FLY FM FO FOO FOOTBALL FORD FOREX FORSALE FORUM FOUNDATION FOX FR FRESENIUS FRL FROGANS FUND FURNITURE FUTBOL FYI GA GAL GALLERY GAME GARDEN GB GBIZ GD GDN GE GEA GENT GENTING GF GG GGEE GH GI GIFT GIFTS GIVES GIVING GL GLASS GLE GLOBAL GLOBO GM GMAIL GMO GMX GN GOLD GOLDPOINT GOLF GOO GOOG GOOGLE GOP GOT GOV GP GQ GR GRAINGER GRAPHICS GRATIS GREEN GRIPE GROUP GS GT GU GUCCI GUGE GUIDE GUITARS GURU GW GY HAMBURG HANGOUT HAUS HEALTH HEALTHCARE HELP HELSINKI HERE HERMES HIPHOP HITACHI HIV HK HM HN HOCKEY HOLDINGS HOLIDAY HOMEDEPOT HOMES HONDA HORSE HOST HOSTING HOTELES HOTMAIL HOUSE HOW HR HSBC HT HU HYUNDAI IBM ICBC ICE ICU ID IE IFM IINET IL IM IMMO IMMOBILIEN IN INDUSTRIES INFINITI INFO ING INK INSTITUTE INSURANCE INSURE INT INTERNATIONAL INVESTMENTS IO IPIRANGA IQ IR IRISH IS ISELECT IST ISTANBUL IT ITAU IWC JAGUAR JAVA JCB JE JETZT JEWELRY JLC JLL JM JMP JO JOBS JOBURG JOT JOY JP JPRS JUEGOS KAUFEN KDDI KE KFH KG KH KI KIA KIM KINDER KITCHEN KIWI KM KN KOELN KOMATSU KP KPN KR KRD KRED KW KY KYOTO KZ LA LACAIXA LAMBORGHINI LAMER LANCASTER LAND LANDROVER LANXESS LASALLE LAT LATROBE LAW LAWYER LB LC LDS LEASE LECLERC LEGAL LEXUS LGBT LI LIAISON LIDL LIFE LIFEINSURANCE LIFESTYLE LIGHTING LIKE LIMITED LIMO LINCOLN LINDE LINK LIVE LIVING LIXIL LK LOAN LOANS LOL LONDON LOTTE LOTTO LOVE LR LS LT LTD LTDA LU LUPIN LUXE LUXURY LV LY MA MADRID MAIF MAISON MAKEUP MAN MANAGEMENT MANGO MARKET MARKETING MARKETS MARRIOTT MBA MC MD ME MED MEDIA MEET MELBOURNE MEME MEMORIAL MEN MENU MEO MG MH MIAMI MICROSOFT MIL MINI MK ML MM MMA MN MO MOBI MOBILY MODA MOE MOI MOM MONASH MONEY MONTBLANC MORMON MORTGAGE MOSCOW MOTORCYCLES MOV MOVIE MOVISTAR MP MQ MR MS MT MTN MTPC MTR MU MUSEUM MUTUELLE MV MW MX MY MZ NA NADEX NAGOYA NAME NAVY NC NE NEC NET NETBANK NETWORK NEUSTAR NEW NEWS NEXUS NF NG NGO NHK NI NICO NINJA NISSAN NL NO NOKIA NORTON NOWRUZ NP NR NRA NRW NTT NU NYC NZ OBI OFFICE OKINAWA OM OMEGA ONE ONG ONL ONLINE OOO ORACLE ORANGE ORG ORGANIC ORIGINS OSAKA OTSUKA OVH PA PAGE PAMPEREDCHEF PANERAI PARIS PARS PARTNERS PARTS PARTY PE PET PF PG PH PHARMACY PHILIPS PHOTO PHOTOGRAPHY PHOTOS PHYSIO PIAGET PICS PICTET PICTURES PID PIN PING PINK PIZZA PK PL PLACE PLAY PLAYSTATION PLUMBING PLUS PM PN POHL POKER PORN POST PR PRAXI PRESS PRO PROD PRODUCTIONS PROF PROMO PROPERTIES PROPERTY PROTECTION PS PT PUB PW PY QA QPON QUEBEC RACING RE READ REALTOR REALTY RECIPES RED REDSTONE REDUMBRELLA REHAB REISE REISEN REIT REN RENT RENTALS REPAIR REPORT REPUBLICAN REST RESTAURANT REVIEW REVIEWS REXROTH RICH RICOH RIO RIP RO ROCHER ROCKS RODEO ROOM RS RSVP RU RUHR RUN RW RWE RYUKYU SA SAARLAND SAFE SAFETY SAKURA SALE SALON SAMSUNG SANDVIK SANDVIKCOROMANT SANOFI SAP SAPO SARL SAS SAXO SB SBS SC SCA SCB SCHAEFFLER SCHMIDT SCHOLARSHIPS SCHOOL SCHULE SCHWARZ SCIENCE SCOR SCOT SD SE SEAT SECURITY SEEK SELECT SENER SERVICES SEVEN SEW SEX SEXY SFR SG SH SHARP SHELL SHIA SHIKSHA SHOES SHOW SHRIRAM SI SINGLES SITE SJ SK SKI SKIN SKY SKYPE SL SM SMILE SN SNCF SO SOCCER SOCIAL SOFTBANK SOFTWARE SOHU SOLAR SOLUTIONS SONY SOY SPACE SPIEGEL SPREADBETTING SR SRL ST STADA STAR STARHUB STATEFARM STATOIL STC STCGROUP STOCKHOLM STORAGE STUDIO STUDY STYLE SU SUCKS SUPPLIES SUPPLY SUPPORT SURF SURGERY SUZUKI SV SWATCH SWISS SX SY SYDNEY SYMANTEC SYSTEMS SZ TAB TAIPEI TAOBAO TATAMOTORS TATAR TATTOO TAX TAXI TC TCI TD TEAM TECH TECHNOLOGY TEL TELEFONICA TEMASEK TENNIS TF TG TH THD THEATER THEATRE TICKETS TIENDA TIFFANY TIPS TIRES TIROL TJ TK TL TM TMALL TN TO TODAY TOKYO TOOLS TOP TORAY TOSHIBA TOURS TOWN TOYOTA TOYS TR TRADE TRADING TRAINING TRAVEL TRAVELERS TRAVELERSINSURANCE TRUST TRV TT TUBE TUI TUSHU TV TW TZ UA UBS UG UK UNIVERSITY UNO UOL US UY UZ VA VACATIONS VANA VC VE VEGAS VENTURES VERISIGN VERSICHERUNG VET VG VI VIAJES VIDEO VILLAS VIN VIP VIRGIN VISION VISTA VISTAPRINT VIVA VLAANDEREN VN VODKA VOLKSWAGEN VOTE VOTING VOTO VOYAGE VU WALES WALTER WANG WANGGOU WATCH WATCHES WEATHER WEBCAM WEBER WEBSITE WED WEDDING WEIR WF WHOSWHO WIEN WIKI WILLIAMHILL WIN WINDOWS WINE WME WORK WORKS WORLD WS WTC WTF XBOX XEROX XIN XN--11B4C3D XN--1QQW23A XN--30RR7Y XN--3BST00M XN--3DS443G XN--3E0B707E XN--3PXU8K XN--42C2D9A XN--45BRJ9C XN--45Q11C XN--4GBRIM XN--55QW42G XN--55QX5D XN--6FRZ82G XN--6QQ986B3XL XN--80ADXHKS XN--80AO21A XN--80ASEHDB XN--80ASWG XN--90A3AC XN--90AIS XN--9DBQ2A XN--9ET52U XN--B4W605FERD XN--C1AVG XN--C2BR7G XN--CG4BKI XN--CLCHC0EA0B2G2A9GCD XN--CZR694B XN--CZRS0T XN--CZRU2D XN--D1ACJ3B XN--D1ALF XN--ECKVDTC9D XN--EFVY88H XN--ESTV75G XN--FHBEI XN--FIQ228C5HS XN--FIQ64B XN--FIQS8S XN--FIQZ9S XN--FJQ720A XN--FLW351E XN--FPCRJ9C3D XN--FZC2C9E2C XN--G2XX48C XN--GECRJ9C XN--H2BRJ9C XN--HXT814E XN--I1B6B1A6A2E XN--IMR513N XN--IO0A7I XN--J1AEF XN--J1AMH XN--J6W193G XN--JLQ61U9W7B XN--KCRX77D1X4A XN--KPRW13D XN--KPRY57D XN--KPU716F XN--KPUT3I XN--L1ACC XN--LGBBAT1AD8J XN--MGB9AWBF XN--MGBA3A3EJT XN--MGBA3A4F16A XN--MGBAAM7A8H XN--MGBAB2BD XN--MGBAYH7GPA XN--MGBB9FBPOB XN--MGBBH1A71E XN--MGBC0A9AZCG XN--MGBERP4A5D4AR XN--MGBPL2FH XN--MGBT3DHD XN--MGBTX2B XN--MGBX4CD0AB XN--MK1BU44C XN--MXTQ1M XN--NGBC5AZD XN--NGBE9E0A XN--NODE XN--NQV7F XN--NQV7FS00EMA XN--NYQY26A XN--O3CW4H XN--OGBPF8FL XN--P1ACF XN--P1AI XN--PBT977C XN--PGBS0DH XN--PSSY2U XN--Q9JYB4C XN--QCKA1PMC XN--QXAM XN--RHQV96G XN--S9BRJ9C XN--SES554G XN--T60B56A XN--TCKWE XN--UNUP4Y XN--VERMGENSBERATER-CTB XN--VERMGENSBERATUNG-PWB XN--VHQUV XN--VUQ861B XN--WGBH1C XN--WGBL6A XN--XHQ521B XN--XKC2AL3HYE2A XN--XKC2DL3A5EE0H XN--Y9A3AQ XN--YFRO4I67O XN--YGBI2AMMX XN--ZFR164B XPERIA XXX XYZ YACHTS YAMAXUN YANDEX YE YODOBASHI YOGA YOKOHAMA YOUTUBE YT ZA ZARA ZERO ZIP ZM ZONE ZUERICH ZW  b   That easily discarded emails like 3c296rD3HNEE d139c a51  Sd sd dox etc  Domain name can be further edited if needed e g  specific country domain etc

User · Answer

Following is the regular expression for validating email address       w     w

User · Answer

There is not one which is really usable  I discuss some issues in my answer to Is there a php library for email address validation   it is discussed also in Regexp recognition of email address hard   In short  don t expect a single  usable regex to do a proper job  And the best regex will validate the syntax  not the validity of an e-mail  jhohn example com is correct but it will probably bounce

User · Answer

It depends on what you mean by best  If you re talking about catching every valid email address use the following          r n     t                 lt  gt               000- 031            r n     t      Z           lt  gt                          r               r n     t             r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n      t            r n     t              r n     t           lt  gt               000- 0 31            r n     t     Z           lt  gt                           r                   r n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                           r                   r n     t               lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n      t       lt        r n     t               lt  gt               000- 031             r n     t     Z           lt  gt                           r                  r n      t                r n     t           lt  gt               000- 031            r n      t     Z           lt  gt                           r                  r n     t                   r n     t           lt  gt               000- 031            r n      t     Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t             lt  gt               000- 031            r n     t      Z           lt  gt                          r               r n     t            r  n     t                r n     t           lt  gt               000- 031             r n     t     Z           lt  gt                          r               r n     t             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         000- 031            r n     t     Z            lt  gt                          r               r n     t            r n     t               r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t       lt        r n      t               lt  gt               000- 031            r n     t     Z            lt  gt                           r                  r n     t                r n      t           lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                  r n      t           lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t            lt  gt               000- 031            r n     t     Z           lt  gt                            r                  r n     t                r n     t              lt  gt               000- 031            r n     t     Z           lt  gt                           r               r n     t            r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                          r               r n     t            r n     t               r n     t           lt  gt               000- 031            r n     t      Z           lt  gt                           r                  r n     t                 r n     t           lt  gt               000- 031            r n     t     Z            lt  gt                           r                  r n     t        gt         r n     t          s      http   www ex-parrot com  pdw Mail-RFC822-Address html  If you re looking for something simpler but that will catch most valid email addresses try something like       a-zA-Z0-9   -    a-zA-Z0-9-     a-zA-Z0-9-        EDIT  From the link      This regular expression will only validate addresses that have had any comments stripped and replaced with whitespace  this is done by the module

User · Answer

I use this         lt  gt              s          lt  gt              s                     0-9  1 3    0-9  1 3    0-9  1 3    0-9  1 3       a-zA-Z -0-9       a-zA-Z  2

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I ve been using this touched up version of your regex for a while and it hasn t left me with too many surprises  I ve never encountered an apostrophe in an email yet so it doesn t validate that  It does validate Jean Fran  ois anydomain museum and                      but not weird abuse of those non alphanumeric characters    you com            amp   -            w d  amp  -        w d  amp  -       w d-       w d-          d  1 3      w  2         It does support IP addresses you 192 168 1 1 but I haven t refined it enough to deal with bogus IP ranges such as 999 999 999 1   It also supports all the TLDs over 3 characters which stops asdf asdf asdf which I think the original let through  I ve been beat  there are too many tlds now over 3 characters   I know acrosman has abandoned his regex but this flavour lives on

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Maybe the best     a-zA-Z0-9    -    a-zA-Z0-9      a-zA-Z0-9    -   a-zA-Z0-9       a-zA-Z  2 7     Start with a letter or number  may include  quot -    quot   end with  quot   quot  and less than 7 characters  such as  company

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The fully RFC 822 compliant regex is inefficient and obscure because of its length   Fortunately  RFC 822 was superseded twice and the current specification for email addresses is RFC 5322   RFC 5322 leads to a regex that can be understood if studied for a few minutes and is efficient enough for actual use   One RFC 5322 compliant regex can be found at the top of the page at http   emailregex com  but uses the IP address pattern that is floating around the internet with a bug that allows 00 for any of the unsigned byte decimal values in a dot-delimited address  which is illegal   The rest of it appears to be consistent with the RFC 5322 grammar and passes several tests using grep -Po  including cases domain names  IP addresses  bad ones  and account names with and without quotes   Correcting the 00 bug in the IP pattern  we obtain a working and fairly fast regex    Scrape the rendered version  not the markdown  for actual code           a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9             2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9       3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          or       a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9             2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9       3     2 5 0-5   0-4  0-9   1 0-9  0-9   1-9   0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          Here is diagram of finite state machine for above regexp which is more clear than regexp itself   The more sophisticated patterns in Perl and PCRE  regex library used e g  in PHP  can correctly parse RFC 5322 without a hitch  Python and C  can do that too  but they use a different syntax from those first two  However  if you are forced to use one of the many less powerful pattern-matching languages  then it   s best to use a real parser   It s also important to understand that validating it per the RFC tells you absolutely nothing about whether that address actually exists at the supplied domain  or whether the person entering the address is its true owner  People sign others up to mailing lists this way all the time  Fixing that requires a fancier kind of validation that involves sending that address a message that includes a confirmation token meant to be entered on the same web page as was the address    Confirmation tokens are the only way to know you got the address of the person entering it  This is why most mailing lists now use that mechanism to confirm sign-ups  After all  anybody can put down president whitehouse gov  and that will even parse as legal  but it isn t likely to be the person at the other end   For PHP  you should not use the pattern given in Validate an E-Mail Address with PHP  the Right Way from which I quote      There is some danger that common usage and widespread sloppy coding will establish a de facto standard for e-mail addresses that is more restrictive than the recorded formal standard    That is no better than all the other non-RFC patterns  It isn   t even smart enough to handle even RFC 822  let alone RFC 5322  This one  however  is   If you want to get fancy and pedantic  implement a complete state engine  A regular expression can only act as a rudimentary filter  The problem with regular expressions is that telling someone that their perfectly valid e-mail address is invalid  a false positive  because your regular expression can t handle it is just rude and impolite from the user s perspective  A state engine for the purpose can both validate and even correct e-mail addresses that would otherwise be considered invalid as it disassembles the e-mail address according to each RFC  This allows for a potentially more pleasing experience  like     The specified e-mail address  myemail address com  is invalid  Did you mean  myemail address com     See also Validating Email Addresses  including the comments  Or Comparing E-mail Address Validating Regular Expressions     Debuggex Demo

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I never bother creating with my own regular expression  because chances are that someone else has already come up with a better version   I always use regexlib to find one to my liking

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According to official standard RFC 2822 valid email regex is       a-z0-9     amp              -        a-z0-9     amp              -           x01- x08 x0b x0c x0e- x1f x21 x23- x5b x5d- x7f      x01- x09 x0b x0c x0e- x7f             a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9            25 0-5  2 0-4  0-9   01   0-9  0-9       3    25 0-5  2 0-4  0-9   01   0-9  0-9    a-z0-9-   a-z0-9       x01- x08 x0b x0c x0e- x1f x21- x5a x53- x7f      x01- x09 x0b x0c x0e- x7f          if you want to use it in Java its really very easy  import java util regex     class regexSample       public static void main String args                  Input the string for validation       String email    xyz hotmail com            Set the email pattern string       Pattern p   Pattern compile       a-z0-9     amp              -         a-z0-9     amp              -                             x01-  x08  x0b  x0c  x0e-  x1f  x21  x23-  x5b  x5d-  x7f       x01-  x09  x0b  x0c  x0e-  x7f                                        a-z0-9     a-z0-9-   a-z0-9         a-z0-9     a-z0-9-   a-z0-9             25 0-5  2 0-4  0-9   01   0-9  0-9        3    25 0-5  2 0-4  0-9   01   0-9  0-9    a-z0-9-   a-z0-9        x01-  x08  x0b  x0c  x0e-  x1f  x21-  x5a  x53-  x7f       x01-  x09  x0b  x0c  x0e-  x7f                    Match the given string with the pattern       Matcher m   p matcher email            check whether match is found        boolean matchFound   m matches           if  matchFound          System out println  Valid Email Id           else         System out println  Invalid Email Id

User · Answer

While deciding which characters are allowed  please remember your apostrophed and hyphenated friends  I have no control over the fact that my company generates my email address using my name from the HR system  That includes the apostrophe in my last name  I can t tell you how many times I have been blocked from interacting with a website by the fact that my email address is  invalid

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There are plenty examples of this out on the net  and I think even one that fully validates the RFC - but it s tens hundreds of lines long if memory serves   People tend to get carried away validating this sort of thing  Why not just check it has an   and at least one   and meets some simple minimum length  It s trivial to enter a fake email and still match any valid regex anyway  I would guess that false positives are better than false negatives

User · Answer

I used      A-Za-z0-9-       A-Za-z0-9-      A-Za-z0-9-      A-Za-z0-9-        A-Za-z  2 4       which includes the capitalized letter as well  You wouldn t even need to use tolowercase in this case

User · Answer

For me the right way for checking emails is    Check that symbol   exists  and before and after it there are some non-  symbols                   Try to send an email to this address with some  activation code   When the user  activated  his email address  we will see that all is right    Of course  you can show some warning or tooltip in front-end when user typed  strange  email to help him to avoid common mistakes  like no dot in domain part or spaces in name without quoting and so on  But you must accept the address  hello world  if user really want it   Also  you must remember that email address standard was and can evolute  so you can t just type some  standard-valid  regexp once and for all times  And you must remember that some concrete internet servers can fail some details of common standard and in fact work with own  modified standard    So  just check    hint user on frontend and send verification emails on given address

[regex] How to validate an email address using a regular expression?

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