Sounds like you have tried everything already, so it would be a hardware escalation: 1-800-821-2797.
I have a problem.
I would to configure my multifunction printer, Xerox VersaLink B7130 with scan to mail.
I just configured my smtp, and port settings correctly and checked that everything was working fine.
I would that everyone use sca to mail, they have to login via their LDAP linked user and password.
And when they use scan to mail, the address "from" on mail, it must be the mail of logged user.
If no one is logged, the scan to mail isn't accessible.