Both servers use Win2003Server. webserver have SP2, database-server SP1.
We use FMS 18.104.22.1686
I can just tell for mail servers on Mac OS X Server, but I assume it is similar for your Windows Server.
SMTP servers are by default locked down to the own IP address (localhost, 127.0.0.1) for accepting messages, so that one can avoid mail spammers to misuse it. Somewhere in the SMTP relay settings the IP address of the database server must be added.