How to validate smtp credentials before sending mail?

.net smtpclient
Manish Gupta picture Manish Gupta · Mar 11, 2010 · Viewed 17.2k times · Source

I need to validate the username and password set in an SmtpClient instance before sending mail. Using this code:

SmtpClient client = new SmtpClient(host);
client.Credentials = new NetworkCredential(username,password);
client.UseDefaultCredentials = false;

// Here I need to verify the credentials(i.e. username and password)
client.Send(mail);

How can I validate whether the user identified by the credentials is allowed to connect and send a mail?

Answer

TomTom picture TomTom · Mar 11, 2010

There is no way.

SmtpClient bascially can not validate the usernamepassword without contacting the serve it connects to.

What you could do is do it outside SmtpClient, by opening a TCP connection to the server... but authentication CAN be complicated depending how the server is configured.

May I ask WHY you need to know that before sending? normal behavior IMHO would be to wrap sending in appropriate error handling to catch exceptions here.

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