Exchange Server 2003 has stopped receiving mail.

Yesterday, after 4 years, my Exchange Server 2003 (sp2) stopped receiving mail. Can send ok. Using the eseutil tool I defraged the database and ran an integrity check – ok. The System and Application logs do not indicate any problems. The informational logs shows everything is running well, plenty of room in the database as well as free drive space.

Mail sent from various web servers do not go through, nor do they fail, so I do not get a error code. Mail sent from different Exchange server, reqesting delivery notification, simply comes back as undeliverable.

I can successfully telnet to the server and deliver a message using the ip address as well as the domain name.

Virus scans are clean and switched out the router just to test.