Gmail Error The SMTP server requires a secure connection or the client was not authenticated The server response was 5 5 1 Authentication Required

Question

I am using following code to send email  The Code works correctly in my local Machine  But on Production server i am getting the error message  var fromAddress   new MailAddress  mymailid gmail com    var fromPassword    xxxxxx   var toAddress   new MailAddress  yourmailid yourdoamain com     string subject    subject   string body    body    System Net Mail SmtpClient smtp   new System Net Mail SmtpClient       Host    smtp gmail com       Port   587      EnableSsl   true      DeliveryMethod   System Net Mail SmtpDeliveryMethod Network      UseDefaultCredentials   false      Credentials   new NetworkCredential fromAddress Address  fromPassword             using  var message   new MailMessage fromAddress  toAddress        Subject   subject      Body   body     smtp Send message     And on my Gmail A c I have received the following email after i ran the code from production server     Hi         Someone recently used your password to try to sign in to your Google   Account mymailid gmail com  This person was using an application such   as an email  client or mobile device        We prevented the sign-in attempt in case this was a hijacker trying to   access your account  Please review the details of the sign-in attempt       Friday  3 January 2014 13 56 08 o clock UTC  IP Address  xxx xx xx xxx    abcd net    Location  Philadelphia PA  Philadelphia  PA  USA      If you do not recognise this sign-in attempt  someone else might be   trying to access your account  You should sign in to your account and   reset your password immediately        Reset password        If this was you and you are having trouble accessing your account    complete the troubleshooting steps listed at   http   support google com mail p client login       Yours sincerely  The Google Accounts team

User · Answer

When you try to send mail from code and you find the error "The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required", than the error might occur due to following cases.

case 1: when the password is wrong

case 2: when you try to login from some App

case 3: when you try to login from the domain other than your time zone/domain/computer (This is the case in most of scenarios when sending mail from code)

There is a solution for each

solution for case 1: Enter the correct password.

solution 1 for case 2: go to security settings at the followig link https://www.google.com/settings/security/lesssecureapps and enable less secure apps . So that you will be able to login from all apps.

solution 2 for case 2:(see https://stackoverflow.com/a/9572958/52277) enable two-factor authentication (aka two-step verification) , and then generate an application-specific password. Use that newly generated password to authenticate via SMTP.

solution 1 for case 3: (This might be helpful) you need to review the activity. but reviewing the activity will not be helpful due to latest security standards the link will not be useful. So try the below case.

solution 2 for case 3: If you have hosted your code somewhere on production server and if you have access to the production server, than take remote desktop connection to the production server and try to login once from the browser of the production server. This will add excpetioon for login to google and you will be allowed to login from code.

But what if you don't have access to the production server. try the solution 3

solution 3 for case 3: You have to enable login from other timezone / ip for your google account.

to do this follow the link https://g.co/allowaccess and allow access by clicking the continue button.

And that's it. Here you go. Now you will be able to login from any of the computer and by any means of app to your google account.

User · Answer

NOVEMBER 2018  have tried everything above with no success   Below is the solution that worked finally  Unfortunately it s not using SSL  but it works     var fromAddress   new MailAddress asd asd com   From Name    var toAddress   new MailAddress  tosend asd com    To Name     const string subject    Subject   const string body    Body    var smtp   new SmtpClient       Host    aspmx l google com       Port   25      EnableSsl   false    using  var message   new MailMessage fromAddress  toAddress        Subject   subject      Body   body          smtp Send message

User · Answer

You might need to create generate a specific APP password from gmail  you app or script will then use this new password instead of your regular password  Your regular password will still work fine for you   That is what did it for me  I still used the same email account but had to generate a new app specific password   https   support google com accounts answer 185833 hl en    Basically you can do it here  https   security google com settings security apppasswords

User · Answer

I tried all of the suggestions found here  from enabling less secure apps  to trying port 587    nothing worked  Finally I just commented out the line UseDefaultCredentials   false  Everything worked if I didn t touch that boolean

User · Answer

You need to turn on  Allow less secure apps  from here  https   myaccount google com lesssecureapps

User · Answer

First  I purchased the domain in GoDaddy  and when I clicked this link https   www google com settings security lesssecureapps I didn t have the option  it show this message  quot The domain administrator manages these settings quot   so I go to the Admin Console https   admin google com  There is this option  Then appears the option that I needed in

User · Answer

just turn on the setting of or gmail  see below given image

User · Answer

If your are using gmail    1-logon to your account   2- browse this link  3- Allow less secure apps  ON   Enjoy

User · Answer

dont put break-point before await smtp SendMailAsync mail         when it waits with a break point giving this error when i remove break point it has worked

User · Answer

I had the same problem for an application deployed to Microsoft Azure      SmtpException  The SMTP server requires a secure connection or the   client was not authenticated  The server response was  5 5 1   Authentication Required    First I approved all unknown devices  some ip-addresses originating from Ireland  on the following page  signed in as the gmail user   https   security google com settings u 1 security secureaccount  I used the following settings for the client   var client   new SmtpClient  smtp gmail com    client Port   587  client EnableSsl   true  client UseDefaultCredentials   false  client Credentials   new NetworkCredential  my user name gmail com    my password       It started working only after I set the following property on the smtp-client   client TargetName    STARTTLS smtp gmail com

User · Answer

This generally happens when you try login from different time zone or IP Address Computer  Your production server and the mail id you have used both are in different time zone  Choose either of these two solutions   1  Log in to production server via remote access  and sign in to gmail once with your credentials  They will ask for the confirmation  confirm it and log out   Or 2  log in gmail to your local computer  Follow this Link and choose review this activity and take proper actions

User · Answer

A comment from Tomasz Madeyski is what fixed my problem    he tells that exists a bug on SetDefaultCredential  him says     The issue is that in UseDefaultCredentials setter there is this code  this transport Credentials   value    ICredentialsByHost  CredentialCache DefaultNetworkCredentials    ICredentialsByHost  null  which overrides credentials set by Credentials setter  For me it looks like SmtpClient s bug   if you put smtpClient UseDefaultCredentials   false after set credentials    this line set to null those credentials

User · Answer

I used all of the above mentioned solutions but it finally worked only after i enabled IMAP Access from Gmail settings Link to Enable IMAP Access in gmail settings  Of course  the points in the other solutions were required too

User · Answer

I have faced the same problem  It happens when you turn on 2 Step Verification  MFA   Just Turn off 2 Step Verification and your problem should be solved

User · Answer

Hi I had the same issue    what I ve done to solve it  is to turn on the less secure app  after connecting to my gmail account  I entered this link  https   www google com settings security lesssecureapps  Then I turn on the secure app and  and the it worked  it has been said also above

User · Answer

I m a google apps for business subscriber and I spend the last couple hours just dealing with this  even after having all the correct settings  smtp  port  enableSSL  etc    Here s what worked for me and the web sites that were throwing the 5 5 1 error when trying to send an email    Login to your admin google com Click SECURITY  lt -- if this isn t visible  then click  MORE CONTROLS   and add it from the list Click Basic Settings Scroll to the bottom of the Basic Settings box  click the link   Go to settings for less secure apps  Select the option  3   Enforce access to less secure apps for all users  Not Recommended  Press SAVE at the bottom of the window   After doing this my email forms from the website were working again   Good luck

User · Answer

I have a previously-working code that throws this error now  No issue on password  No need to convert message to base64 either  Turns out  i need to do the following    Turn off 2-factor authentication Set  Allow less secure apps  to ON Login to your gmail account from production server Go here as well to approve the login activity Run your app in production server   Working code      public static void SendEmail string emailTo  string subject  string body                var client   new SmtpClient  smtp gmail com   587                        Credentials   new NetworkCredential  youremail gmail com    secretpassword                EnableSsl   true                     client Send  youremail gmail com   emailTo  subject  body           Turning off 2-factor authentication   Set  Allow less secure apps  to ON  same page  need to scroll to bottom

User · Answer

Just follow the step in the google email and enable less secure apps

User · Answer

Below is my code I also had the same error but the problem was that i gave my password wrong The below code will work perfectly  try it              MailMessage mail   new MailMessage                SmtpClient SmtpServer   new SmtpClient  smtp gmail com                             mail From   new MailAddress  fromaddress gmail com                mail To Add  toaddress1 gmail com                mail To Add  toaddress2 gmail com                mail Subject    Password Recovery                mail Body       lt html gt                mail Body      lt body gt                mail Body      lt table gt                mail Body      lt tr gt                mail Body      lt td gt User Name    lt  td gt  lt td gt  HAi  lt  td gt                mail Body      lt  tr gt                 mail Body      lt tr gt                mail Body      lt td gt Password    lt  td gt  lt td gt aaaaaaaaaa lt  td gt                mail Body      lt  tr gt                mail Body      lt  table gt                mail Body      lt  body gt                mail Body      lt  html gt                mail IsBodyHtml   true              SmtpServer Port   587              SmtpServer Credentials   new System Net NetworkCredential  sendfrommailaddress com    password                SmtpServer EnableSsl   true              SmtpServer Send mail     You can refer it in my blog

User · Answer

You should disallow less secure apps to access your google account   to do   https   myaccount google com lesssecureapps

User · Answer

try changing the host  this is the new one  I got this configuring mozilla thunderbird  Host    smtp googlemail com    that work for me

User · Answer

I have really looked at a lot of ideas  the only solution was this way  works with different email Providers               try                       ViewProgressbar  quot Try to connect mail-server    quot   progressBar1 Value   20               string host   dsProvider Rows y   quot POP hostOut quot   ToString                int port   int Parse dsProvider Rows y   quot POP portOut quot   ToString        587             string   email   von1 Split                   string userName    dsProvider Rows y   quot login quot   ToString       quot email 0  email 1  quot    email 0   quot   quot  email 1    email 0               string password   layer getUserPassword listSender SelectedValue ToString                 SmtpClient client   new SmtpClient host  port               client DeliveryMethod   SmtpDeliveryMethod Network              client UseDefaultCredentials   false                A idea from MSDN but it not works  You got  quot The server response was  5 5 1 Authentication Required  quot                System Net NetworkCredential myCreds   new System Net NetworkCredential userName  password  host                 System Net CredentialCache cache   new System Net CredentialCache                  cache Add host  port   quot NTLM quot   myCreds                  cache GetCredential host  port   quot NTLM quot        NTLM             client Credentials   new System Net NetworkCredential userName  password               client Host   host              client Port   port              client EnableSsl   true              client Send message               ViewProgressbar                      catch  SmtpException ex

User · Answer

Its a security issue  Gmail by default prevents access for your e-mail account from custom applications  You can set it up to accept the login from your application   After Logging in to your e-mail  CLICK HERE  This will take you to the following page

User · Answer

After spending a couple of hours today trying every solution here  I was still unable to get past this exact error  I have used gmail many times in this way so I knew it was something dumb  but nothing I did fixed the problem  I finally stumbled across the solution in my case so thought I would share   First  most of the answers above are also required  but in my case  it was a simple matter of ordering of the code while creating the SmtpClient class   In this first code snippet below  notice where the Credentials   creds line is located  This implementation will generate the error referenced in this question even if you have everything else set up properly   System Net Mail SmtpClient client   new System Net Mail SmtpClient       Host   Emailer Host      Port   Emailer Port      Credentials   creds      EnableSsl   Emailer RequireSSL      UseDefaultCredentials   false      DeliveryMethod   System Net Mail SmtpDeliveryMethod Network     However  if you move the Credentials setter call to the bottom  the email will be sent without error  I made no changes to the surrounding code   ie   the username password  etc  Clearly  either the EnableSSL  UseDefaultCredentials  or the DeliveryMethod is dependent on the Credentials being set first    I didn t test all to figure out which one it was though   System Net Mail SmtpClient client   new System Net Mail SmtpClient       Host   Emailer Host      Port   Emailer Port      EnableSsl   Emailer RequireSSL      UseDefaultCredentials   false      DeliveryMethod   System Net Mail SmtpDeliveryMethod Network      Credentials   creds     Hope this helps save someone else some headaches in the future

User · Answer

What worked for me was to activate the option for less secure apps  I am using VB NET   Public Shared Sub enviaDB ByRef body As String  ByRef file location As String          Dim mail As New MailMessage           Dim SmtpServer As New SmtpClient  smtp gmail com           mail From   New MailAddress  from gmail com           mail  To  Add  to gmail com           mail Subject    subject          mail Body   body         Dim attachment As System Net Mail Attachment         attachment   New System Net Mail Attachment file location          mail Attachments Add attachment          SmtpServer Port   587         SmtpServer Credentials   New System Net NetworkCredential  user    password           SmtpServer EnableSsl   True         SmtpServer Send mail      End Sub   So log in to your account and then go to  google com settings security lesssecureapps

[c#] Gmail Error :The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required

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