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The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first. r3sm3412459ibk.1

this error is coming when send a email
Updated 9-Jan-23 2:53am
Henry Minute 3-Oct-10 6:09am    
When you send email from where. Your own program, a commercial Email programme or where? How can you expect people to help you if you do not give them complete information?

1 solution

Try to enable ssl before sending the message, something like this:

SmtpClient smtpClient= new SmtpClient();
  smtpClient.EnableSsl = true;
catch (Exception e)
  MessageBox.Show(e.Message, MessageBoxButtons.OK, MessageBoxIcon.Error);

Good luck!
Share this answer
VinodKumar01 4-Oct-10 0:39am    
where is MessageBox class
E.F. Nijboer 4-Oct-10 3:52am    

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