SMTP Problems on Small Business Server?

MSExchange.org has a great little article on Using SMTPDIAG to Diagnose Exchange 2003 Related SMTP and DNS Problems.

A lot of questions in the SBS space come up about SMTP routing and getting it set up properly. Obviously there are a lot of ways to check and see if your SMTP is working correctly. SMTPDIAG is a great little utility to see just that. Run it from a remote system to make sure that your new SBS System is up and running properly or perhaps to diagnose a recent problem with a mail recipient.

Probably the first thing that is quick and easy and that is most often missed is trying a telnet on port 25. Many techs or first time SBS users miss this step. Try it now from a remote system and you will see what we're talking about. On a remote system go to a command prompt and type telnet mail.yourdomain.com 25 where mail.yourdomain.com is the fully qualified domain name of your SBS machine. You should get a response back that SMTP is indeed working. If not, something is wrong. My next post will give you a tip on what could be the possible problem.