This article was the best! I'm an idiot and now I've got my very own mail server. YEHAW! Anyway, to my question:
I'm using my Airport Base Station as a router to handle internet access for my Macs at home. The other Macs are wired and log into my G4 to get mail. I have no problems sending mail to any local account, however, when I try to send email outside (using my system as the outgoing mail server) the message never gets delivered. I've included the 'Behind a firewall' and 'Lame ISP' lines in the config.mc file, but no go.