Sending email through Gmail SMTP server with C

Question

For some reason neither the accepted answer nor any others work for me for  Sending email in  NET through Gmail   Why would they not work   UPDATE  I have tried all the answers  accepted and otherwise  in the other question  but none of them work   I would just like to know if it works for anyone else  otherwise Google may have changed something  which has happened before    When I try the piece of code that uses SmtpDeliveryMethod Network  I quickly receive an SmtpException on Send message   The message is      The SMTP server requires a secure connection or the client was not authenticated     The server response was       5 5 1 Authentication Required  Learn more at   lt -- seriously  it ends there    UPDATE   This is a question that I asked a long time ago  and the accepted answer is code that I ve used many  many times on different projects   I ve taken some of the ideas in this post and other EmailSender projects to create an EmailSender project at Codeplex  It s designed for testability and supports my favourite SMTP services such as GoDaddy and Gmail

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Oh   It s amazing    First I Couldn t send an email for any reasons  But after I changed the sequence of these two lines as below  it works perfectly      1  client UseDefaultCredentials   true     2  client Credentials   new System Net NetworkCredential  username gmail com    password      Hope this help

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Another thing that I ve found is that you must change your password at least once  And try to use a secure level password  do not use the same user as password  123456  etc

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I ve had some problems sending emails from my gmail account too  which were due to several of the aforementioned situations  Here s a summary of how I got it working  and keeping it flexible at the same time    First of all setup your GMail account    Enable IMAP and assert the right maximum number of messages  you can do so here  Make sure your password is at least 7 characters and is strong  according to Google  Make sure you don t have to enter a captcha code first  You can do so by sending a test email from your browser   Make changes in web config  or app config  I haven t tried that yet but I assume it s just as easy to make it work in a windows application        lt configuration gt       lt appSettings gt           lt add key  EnableSSLOnMail  value  True   gt          lt  appSettings gt        lt  -- other settings -- gt                  lt  -- system net settings -- gt       lt system net gt           lt mailSettings gt               lt smtp from  yourusername gmail com  deliveryMethod  Network  gt                   lt network                      defaultCredentials  false                       host  smtp gmail com                       port  587                       password  stR0ngPassW0rd                       userName  yourusername gmail com                        gt                   lt  -- When using  Net 4 0  or later  add attribute  enableSsl  true  and you re all set-- gt               lt  smtp gt           lt  mailSettings gt       lt  system net gt   lt  configuration gt      Add a Class to your project   Imports System Net Mail  Public Class SSLMail      Public Shared Sub SendMail ByVal e As System Web UI WebControls MailMessageEventArgs           GetSmtpClient Send e Message            Since the message is sent here  set cancel true so the original SmtpClient will not try to send the message too          e Cancel   True      End Sub      Public Shared Sub SendMail ByVal Msg As MailMessage          GetSmtpClient Send Msg      End Sub      Public Shared Function GetSmtpClient   As SmtpClient          Dim smtp As New Net Mail SmtpClient          Read EnableSSL setting from web config         smtp EnableSsl   CBool ConfigurationManager AppSettings  EnableSSLOnMail            Return smtp     End Function  End Class   And now whenever you want to send emails all you need to do is call SSLMail SendMail   e g  in a Page with a PasswordRecovery control   Partial Class RecoverPassword Inherits System Web UI Page  Protected Sub RecoverPwd SendingMail ByVal sender As Object  ByVal e As System Web UI WebControls MailMessageEventArgs  Handles RecoverPwd SendingMail     e Message Bcc Add  webmaster example com       SSLMail SendMail e  End Sub  End Class   Or anywhere in your code you can call   SSLMail SendMail New system Net Mail MailMessage  from from com   to to com    Subject    Body      I hope this helps anyone who runs into this post   I used VB NET but I think it s trivial to convert it to any  NET language

User · Answer

I ran into this same error    The SMTP server requires a secure connection or the client was not authenticated  The server response was  5 5 1 Authentication Required  Learn more at    and found out that I was using the wrong password  I fixed the login credentials  and it sent correctly   I know this is late  but maybe this will help someone else

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I m not sure which  NET version is required for this because eglasius mentioned there is no matching enableSsl setting  I m using  NET 4 0  but I suspect it to work in  NET 2 0 or later   but this configuration justed worked for me  and doesn t require you to use any programmatic configuration     lt system net gt     lt mailSettings gt       lt smtp from  myusername gmail com  deliveryMethod  Network  gt         lt network defaultCredentials  false  enableSsl  true  host  smtp gmail com  port  587  password  password  userName  myusername gmail com   gt       lt  smtp gt     lt  mailSettings gt   lt  system net gt    You might have to enable POP or IMAP on your Gmail account first  https   mail google com mail  shva 1 settings fwdandpop  I recommend trying it with a normal mail client first

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I also found that the account I used to log in was de-activated by google for some reason   Once I reset my password  to the same as it used to be   then I was able to send emails just fine   I was getting 5 5 1 message also

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I had also try to many solution but make some changes it will work  host   smtp gmail com port   587 username   email gmail com password   password enabledssl   true   with smtpclient above parameters are work in gmail

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Simple steps to fix this   1 Sign in to your Gmail  2 Navigate to this page https   www google com settings security lesssecureapps  amp  set to  Turn On

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THE FOLLOWING WILL ALMOST CERTAINLY BE THE ANSWER TO YOUR QUESTION IF ALL ELSE HAS FAILED   I got the exact same error  it turns out Google s new password strengh measuring algorithm has changed deeming my current password as too weak  and not telling me a thing about it  not even a message or warning     How did I discover this  Well  I chose to change my password to see if it would help  tried everything else to no avail  and when I changed my password  it worked   Then  for an experiment  I tried changing my password back to my previous password to see what would happen  and Gmail didn t actually allow me to do this  citing the reason  sorry we cannot allow you to save this change as your chosen password is too weak  and wouldn t let me go back to my old password  I figured from this that it was erroring out because either a  you need to change your password once every x amount of months or b   as I said before  their password strength algorithms changed and therefore the weak password i had was not accepted  even though they did not say anything about this when trying to login ANYWHERE  This  number 2  is the most likely scenario  as my weak password was about 4 months old  and it let me use it in Gmail   It s pretty bad that they said nothing about this  but it makes sense  Because most hijacked emails are logged into using software outside of gmail  and I m guessing you are required to have a stronger password if you want to use Gmail outside of the Gmail environment   I hope this helps

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I was using corporate VPN connection  It was the reason why I couldn t send email from my application  It works if I disconnect from VPN

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If you have 2-Step Verification step up on your Gmail account  you will need to generate an App password   https   support google com accounts answer 185833 p app passwords sa amp hl en amp visit id 636903322072234863-1319515789 amp rd 1  Select How to generate an App password option and follow the steps provided  Copy and paste the generated App password somewhere as you will not be able to recover it after you click DONE

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First check your gmail account setting  amp  turn On from  Access for less secure apps        We strongly recommend that you use a secure app  like Gmail  to access your account  All apps made by Google meet these security standards  Using a less secure app  on the other hand  could leave your account vulnerable  Learn more     Set   smtp UseDefaultCredentials   false    before   smtp Credentials   new NetworkCredential fromAddress  fromPassword

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Turn On Access For Less Secure Apps and it will work for all no need to change password    Link to Gmail Setting

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If nothing else has worked here for you you may need to allow access to your gmail account from third party applications  This was my problem  To allow access do the following    Sign in to your gmail account  Visit this page https   accounts google com DisplayUnlockCaptcha and click on button to allow access  Visit this page https   www google com settings security lesssecureapps and enable access for less secure apps    This worked for me hope it works for someone else

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Andres Pompiglio  Yes that s right you must change your password at least once   this codes works just fine     Satrt Send Email Function public string SendMail string toList  string from  string ccList      string subject  string body         MailMessage message   new MailMessage        SmtpClient smtpClient   new SmtpClient        string msg   string Empty      try               MailAddress fromAddress   new MailAddress from           message From   fromAddress          message To Add toList           if  ccList    null  amp  amp  ccList    string Empty              message CC Add ccList           message Subject   subject          message IsBodyHtml   true          message Body   body             We use gmail as our smtp client         smtpClient Host    smtp gmail com              smtpClient Port   587          smtpClient EnableSsl   true          smtpClient UseDefaultCredentials   true          smtpClient Credentials   new System Net NetworkCredential               Your Gmail User Name    Your Gmail Password             smtpClient Send message           msg    Successful lt BR gt              catch  Exception ex                msg   ex Message            return msg      End Send Email Function   AND you can make a call to the function by using   Response Write SendMail recipient Address   UserName gmail com    ccList if any    subject    body

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I had the same problem  but it turned out to be my virus protection was blocking outgoing  spam  email  Turning this off allowed me to use port 587 to send SMTP email via GMail

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Dim SMTPClientObj As New Net Mail SmtpClient SMTPClientObj UseDefaultCredentials   False SMTPClientObj Credentials   New System Net NetworkCredential  myusername gmail com    mypwd   SMTPClientObj Host    smtp gmail com  SMTPClientObj Port   587 SMTPClientObj EnableSsl   True SMTPClientObj Send  myusername gmail com   yourusername gmail com   test   testbody     If you get an error like  The SMTP server requires a secure connection or the client was not authenticated  The server response was  5 5 1 Authentication Required  Learn more at  as I get before this  make sure the line SMTPClientObj UseDefaultCredentials   False included and this line should before the SMTPClientObj Credentials   I did try to switch these 2 lines the opposite way and the 5 5 1 Authentication Required error returned

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You can also connect via port 465  but due to some limitations of the System Net Mail namespace you may have to alter your code  This is because the namespace does not offer the ability to make implicit SSL connections  This is discussed at http   blogs msdn com b webdav 101 archive 2008 06 02 system-net-mail-with-ssl-to-authenticate-against-port-465 aspx  and I have supplied an example of how to use the CDO  Collaborative Data Object  in another discussion  GMail SMTP via C   Net errors on all ports

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Turn on less secure apps for your account  https   www google com settings security lesssecureapps

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I had this problem resolved  Aparently that message is used in multiple error types  My problem was that i had reached my maximum of 500 sent mails   log into the account and manually try to send a mail  If the limit has been reached it will inform you

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CVertex  make sure to review your code  and  if that doesn t reveal anything  post it  I was just enabling this on a test ASP NET site I was working on  and it works    Actually  at some point I had an issue on my code  I didn t spot it until I had a simpler version on a console program and saw it was working  no change on the Gmail side as you were worried about   The below code works just like the samples you referred to   using System  using System Collections Generic  using System Linq  using System Text  using System Net Mail  using System Net   namespace ConsoleApplication2       class Program               static void Main string   args                        var client   new SmtpClient  smtp gmail com   587                                Credentials   new NetworkCredential  myusername gmail com    mypwd                    EnableSsl   true                            client Send  myusername gmail com    myusername gmail com    test    testbody                Console WriteLine  Sent                Console ReadLine                        I also got it working using a combination of web config  http   msdn microsoft com en-us library w355a94k aspx and code  because there is no matching EnableSsl in the configuration file

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One or more reasons are there for these error    Log in with your Gmail  or any other if   in your local system  Also check for Less Secure App and Set it to  Turn On  here is the Link for GMAIL  https   www google com settings security lesssecureapps check for EnableSsl in your Email code  and also set it to true   smtp EnableSsl   true   Also check which port are you using currently  25 is Global  but you can check it for others too like 587   check here  Does all SMTP communication happen over 25  IF YOU ARE ON REMOTE   Check the answer of Vlad Tamas above

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smtp Host    smtp gmail com     host name smtp Port   587    port number smtp EnableSsl   true    whether your smtp server requires SSL smtp DeliveryMethod   System Net Mail SmtpDeliveryMethod Network  smtp Credentials   new NetworkCredential fromAddress  fromPassword   smtp Timeout   20000

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Yet another possible solution for you  I was having similar problems connecting to gmail via IMAP  After trying all the solutions that I came across that you will read about here and elsewhere on SO  eg  enable IMAP  enable less secure access to your mail  using https   accounts google com b 0 displayunlockcaptcha and so on   I actually set up a new gmail account once more    In my original test  the first gmail account I had created  I had connected to my main gmail account  This resulted in erratic behaviour where the wrong account was being referenced by google  For example  running https   accounts google com b 0 displayunlockcaptcha opened up my main account rather than the one I had created for the purpose    So when I created a new account and did not connect it to my main account  after following all the appropriate steps as above  I found that it worked fine   I haven t yet confirmed this  ie  reproduced   but it apparently did it for me   hope it helps

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This code works for me  and also allows in gmail access from unsecure apps  and removing authentication in 2 steps  Host    quot smtp gmail com quot   Port   587  EnableSsl   true  DeliveryMethod   System Net Mail SmtpDeliveryMethod Network  UseDefaultCredentials   false  Credentials   new NetworkCredential MailAddress  Password

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The problem is not one of technical ability to send through gmail   That works for most situations   If you can t get a machine to send  it is usually due to the machine not having been authenticated with a human at the controls at least once   The problem that most users face is that Google decides to change the outbound limits all the time   You should always add defensive code to your solution   If you start seeing errors  step off your send speed and just stop sending for a while   If you keep trying to send Google will sometimes add extra time to your delay period before you can send again   What I have done in my current system is to send with a 1 5 second delay between each message   Then if I get any errors  stop for 5 minutes and then start again   This usually works and will allow you to send up to the limits of the account  last I checked it was 2 000 for premier customer logins per day

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Change your gmail password and try again  it should work after that   Don t know why  but every time you change your hosting you have to change your password

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I was getting the same error and none of the above solutions helped   My problem was that I was running the code from a remote server  which had never been used to log into the gmail account    I opened a browser on the remote server and logged into gmail from there  It asked a security question to verify it was me since this was a new location  After doing the security check I was able to authenticate through code

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In addition to the other troubleshooting steps above  I would also like to add that if you have enabled two-factor authentication  also known as two-step verification  on your GMail account  you must generate an application-specific password and use that newly generated password to authenticate via SMTP   To create one  visit  https   www google com settings  and choose Authorizing applications  amp  sites to generate the password

[c#] Sending email through Gmail SMTP server with C#

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