OP: I did the same thing... running a server for anything is the best way to get started in Linux..

I did a little write up on my "crazy ass email setup" here: http://julian.tosh.us/2010/01/my-crazyass-email-setup/

It's evolved a bit since then and addresses gst's point... I've recently added regular expressions to my postfix maps so an email must match a certain pattern to get through... so it's more like a moderated catchall domain.