I get junk mail from different domains all the time - the easiest way to stop them is just to add a filter to your incoming mail server to either bounce them (uses more resources, but can help diagnose problems) or delete them (usually by sending them to /dev/null).

These two pages on attrition.org might be useful:
http://www.attrition.org/attrition/warn.html - How they block emails (guidelines etc.)
Who to complain to

You might want to take up some of their policies on blocking email, since many spammers don't conform to RFCs when sending mail, or follow their chain of command for reporting abuse (obviously substituting the correct addresses for the domains you are complaining about).