NMSportster, i think that many of us will need to get a better idea what you are trying to do before we can help.
if you want all the different domains to go to the same IP address, then simply put...

open up a terminal and do this:
tail -f /var/log/maillog

now, try to send mail to the machine from an outside source. do you see anything appearing in your mail log? if so, then it should...