I am running a new Exchange 2007 SP1 system. I moved the mailboxes from the old Exchange 2003 server, and incoming mail is working.
But outgoing mail is not working at all; even inside my domain.
Lots of debugging and searching lead me to believe that the problem is that the "Microsoft Exchange Mail Submission Service" (AKA MSExchangeMailSubmission) is not running.
In fact, it's not even listed in the Services list.
This document (http://technet.microsoft.com/en-us/library/aa998342.aspx) says that this service is installed by the Mailbox server role. My server is running the Mailbox role, as well as the Hub Transport and Client Access roles.
How do I get this service to show up in the list, so that I can start it up?