Having just set up a new mailserver, I can attest to the fact that spam is not always evil. A way you can definitely know your shiney new mailserver works is by what is basically now a constant on the Internet -- spam!
Surely enough, once I'd changed the MX records, bogus mail slowly started trickling in. I don't think I've ever been so happy to see spam in my life.
Now just to figure out how to effectively block it...