SMTP mail transfer error authentication

mevada kamlesh

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

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Net.Mail.SmtpException: 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

Source Error:

Line 53: }; Line 54: SMTP.EnableSsl = true; Line 55: SMTP.Send(PassRecMail); Line 56: Line 57: lblPassRec.Text = "Check your email to reset your password.";

Source File: e:\My Website\firstWebsite\ForgotPassword.aspx.cs Line: 55

2 Replies

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Sankara Krishnan Venugopal8y ago
HI Medava,

You may have enabled the "double checking authentication" in your gmail/yahoo/outlook account
Update the below code in your program and check it
client.UseDefaultCredentials = true;
and update the
var client = new SmtpClient();
client.EnableSsl = client.Port == 587 || client.Port == 465;
Works for me in .net 4.0

Thanks!
mevada kamlesh8y ago
Already On less Secure App option but not solve my problem please help us