I changed the IP address on my Exchange 2000 server and now it won't receive messages from external domains. Internally it works fine. It will send and receive internal emails, and send external emails. It has a hard coded IP address and was able to be pinged after the address change. I also restarted it after the address change.
One other symptom it had is that it would not accept a telnet session after the address change.
I gave up trying to fix it and set the IP address back to the original address and now everything's working except I still need to give it a new address.