AuthenticationException being thrown for non-authentication issues?

[oatsoda]

I am using the AuthenticationException to track when I think that the credentials are wrong, assuming that it would only throw when the SMTP Response Code are SmtpStatusCode.AuthenticationInvalidCredentials etc. but it seems that in actual fact this exception type can be thrown for any failure - is this correct?

Looking at the code all errors are thrown as an AuthenticationException:

MailKit/MailKit/Net/Smtp/SmtpClient.cs

Lines 733 to 738 in 6d21ecd

	var message = string.Format ("{0}: {1}", response.StatusCode, response.Response);
	if (saslException != null)
	authException = new AuthenticationException (message, saslException);
	else
	authException = new AuthenticationException (message);

The description suggests otherwise:

MailKit/MailKit/Net/Smtp/SmtpClient.cs

Lines 636 to 638 in 6d21ecd

	/// <exception cref="MailKit.Security.AuthenticationException">
	/// Authentication using the supplied credentials has failed.
	/// </exception>

I believe that I am getting AuthenticationExceptions with messages such as:

ServiceNotAvailable: 4.3.2 Service not active [AM6PR03CA0003.eurprd03.prod.outlook.com].

Which is problematic as the AuthenticationException does not have an StatusCode which I could inspect for more details.

How should I be detecting true failures of credentials?

[jstedfast]

You could try digging into the InnerException property. That should have the info you are looking for.

AuthenticationException -> SaslException -> SmtpCommandException

[oatsoda]

Thanks @jstedfast. Will take a look.

[jstedfast]

If the InnerException suggestion doesn’t work, let me know and I’ll try to look into making changes to the code so you can get that info.

[jstedfast]

It looks like my suggestion won't work now that I am looking at the code.

I'll commit a fix shortly.

[jstedfast]

FWIW, the nesting goes like this: AuthenticationException -> SmtpCommandException [ -> SaslException ]

[oatsoda]

@jstedfast Thanks for following up on this. I had just begun to look at how to get this working. I guess I will need to take the next version with the fix in!

So ultimately I can check for password/account specific failures by:

• Checking for AuthenticationException
• Checking it has an InnerException of type SmtpCommandException
• Checking the StatusCode on the InnerException

Do you have an ETA on the next release of MailKit?

[jstedfast]

Probably not for a few weeks unless a major bug comes to my attention. I try to release every 4-6 weeks or so and I just made a release last week?

[oatsoda]

@jstedfast Any chance of a it being quicker? I'm fighting quite a major live issue with this :(

[jstedfast]

If I have time this weekend, I'll look into it. In the meantime, donations are welcome :)

[RickVM]

Running into the same problem. I would like some way to figure out what went wrong if authentication fails.

InnerException is Null, Message is: "Login failed"

@jstedfast could you reopen this issue and look into it please?

[jstedfast]

The text "Login failed" likely came from the IMAP, POP3 or SMTP server.

You can get a protocol log like this:

using (var client = new SmtpClient (new ProtocolLogger ("smtp.log"))

Replace "Smtp" with Pop3 or Imap depending on what client you are having this issue with.