For some reason my SMTP has ceased to work. This is a Linux based system, and I can send mail fine internally (using Suirrelmail from one account on the server to another), but I can't send to the "outside world".

No settings have been changed, it just simply happened. It seems like port 25 just isn't working.

My server is in the Savvis center.

What's your MTA? Got firewall? Can you receive mail from the outwise world? Can you retrieve mail already on the server (POP3/IMAP)?

God, and email problems, are in the details. :)