I setup Email Transport Method as SMTP and specified a username/password from our local mail server, and double checked it. I do this quit often with various applications, so I'm not sure why it's not working.
I used my own GMail Account and it exists.
We are running our own mail server. Smartermail.
Zend_Mail_Protocol_Exception: Email to email@example.com failed: <firstname.lastname@example.org> No such user here - library\Zend\Mail\Protocol\Abstract.php:431