for my understanding, is this the email configuration for sending out error information? Not a sensor itself?
Could it be, that your using the wrong SMTP Server or wrong credentials.
"Unauthorized" shows this to me.
At gmail i would use smtp.gmail.com as Relay with "[email protected] or [email protected]" and the right password. Try to login in a browser to verify the credentials are right.
If this won't work, please write down your configuration, but without your user information... don't write your credentials open readable ;).