Nice thought, tried the append device domain setting unchecked and checked. No luck.
My exchange server bounces back this message event ID 1026 in the Application log from the source MSExchangeTransport , specifc names not included:
SMTP rejected a (P1) mail from 'domain\user@server.domain.com' with 'Internal Relay Authenticated <Exchange Hub name> ' connector. The user 'domain\user' does not have permissions to send as this address.
The couple more I tried, the domain\user setting is set to use the address I provided in the WorkCentre email address box, which is user@domain.com