5 7 57 SMTP - Client was not authenticated to send anonymous mail during MAIL FROM error

Question

I have to send mails using my web application  Given the below code showing The SMTP server requires a secure connection or the client was not authenticated  The server response was       5 7 57 SMTP  Client was not authenticated to send anonymous mail during MAIL FROM    Help me to find a proper solution  Thank you   Code   protected void btnsubmit Click object sender  EventArgs e         Ticket MailTableAdapters tbl TicketTableAdapter tc     tc   new Ticket MailTableAdapters tbl TicketTableAdapter       DataTable dt   new DataTable       dt   tc GetEmail dpl cate SelectedValue      foreach  DataRow row in dt Rows            string eml    row  Emp Email   ToString         var fromAddress    emailAddress       var toAddress   eml      const string fromPassword                string body    Welcome         smtp settings     var smtp   new System Net Mail SmtpClient                      smtp Host    smtp office365 com            smtp Port   587           smtp EnableSsl   true            smtp DeliveryMethod   System Net Mail SmtpDeliveryMethod Network           smtp Credentials   new NetworkCredential fromAddress  fromPassword            smtp UseDefaultCredentials   false           smtp Timeout   600000                Passing values to smtp object      smtp Send fromAddress  toAddress  subject  body

User · Answer

I use to have the same problem   Add the domain solved it    mySmtpClient Credentials   New System Net NetworkCredential  email domain com    password    domain com

User · Answer

Reshma- In case you have not figured it yet  here are below things that I tried and it solved the same issue    Make sure that NetworkCredentials you set are correct  For example in my case since it was office SMTP  user id had to be used in the NetworkCredential along with domain name and not actual email id  You need to set  UseDefaultCredentials  to false first and then set Credentials  If you set  UseDefaultCredentials  after that it resets the NetworkCredential to null    Hope it helps

User · Answer

In my case  2 Factor Authentication was turned on for the FROM account in Office 365   Once that was turned off  the email sent successfully

User · Answer

Main two reasons only as mentioned in above comments   NetworkCredentials you set should be correct  Verify with try actually signing into the account  You need to set UseDefaultCredentials to false first and then set Credentials Or Put smtp UseDefaultCredentials   false  above the smtp Credentials assignment

User · Answer

Try resetting your password for the email used  Had similar issue  and got it fixed only after changing password

User · Answer

In my situation  our IT department made MFA mandatory for our domain  This means we can only use option 3 in this Microsoft article to send email  Option 3 involves setting up an SMTP relay using an Office365 Connector

User · Answer

Probably the password of the account that you trying to send e-mail is expired  Just check your password policy expire date

User · Answer

I spent way too much time on this and the solution was super simple  I had to use my  MX  as the host and port 25           var sClient   new SmtpClient  domain-com mail protection outlook com            var message   new MailMessage             sClient Port   25          sClient EnableSsl   true          sClient Credentials   new NetworkCredential  user    password            sClient UseDefaultCredentials   false           message Body    Test           message From   new MailAddress  test test com            message Subject    Test           message CC Add new MailAddress  dude good com              sClient Send message

User · Answer

If you are using office 365 follow this steps    check the password expiration time using Azure power shell  Get-MsolUser -All   select DisplayName  LastPasswordChangeTimeStamp Change the password using a new password  not the old one   You can eventually go back to the old password but you need to change it twice    Hope it helps

User · Answer

In my case I was using the MailMessage constructor that takes two strings  to  from  and getting the same error  When I used the default constructor and then added a MailAddress object to the To property of the MailMessage it worked fine

User · Answer

You seem to be passing the From address as emailAddress  which is not a proper email address  For Office365 the From needs to be a real address on the Office365 system  You can validate that if you hardcode your email address as the From and your Office 365 password  Don t leave it there though of course

User · Answer

This is an old question but since this is the first result in google for this error  I thought I would update my progress in this issue   I spent way too may hours on this issue  In the end I had to change my Office 365 account s password few times until my code succeeded in sending emails   Didn t have to make any changes in code

User · Answer

If you reorder your code this way  it should work  SmtpClient client   new SmtpClient    client UseDefaultCredentials   false  client Credentials   new System Net NetworkCredential mailOut  pswMailOut   client Port   587     25 587 client Host    quot smtp office365 com quot   client DeliveryMethod   SmtpDeliveryMethod Network  client EnableSsl   true   MailMessage mail   new MailMessage                mail From   new MailAddress mailOut  displayNameMailOut   mail To Add new MailAddress mailOfTestDestine    mail Subject    quot A special subject quot   mail Body   sb ToString     client Send mail

User · Answer

Set the User default credentials to true   smtp UseDefaultCredentials   True   Before that  input your credential  smtp Credentials   new NetworkCredential fromAddress  fromPassword    This should work fine

User · Answer

Started working after adding property   mail smtp starttls enable true   Using   mail smtp host smtp office365 com mail smtp port 587 mail transport protocol smtp mail smtp auth true mail smtp starttls enable true mail smtp user xxx example com mail smtp password xxx mail smtp from yyy example com

User · Answer

I changed the Office365 password and then tried to send a test email and it worked like a charm for me   I used the front end  database mail option  and settings as smtp office365 com port number 587 and checked the secure connection option  use basic authentication and store the credentials  Hope this turns out useful for someone

[c#] 5.7.57 SMTP - Client was not authenticated to send anonymous mail during MAIL FROM error

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