SMTP service was resolved here:
Now it is on to dovecot. My primary goal is to have POP3 and IMAP services up and running as quickly as possible. My secondary goal is to use APOP and POP-before-SMTP authentication to limit the users who can send email through my server. I've not looked at much dovecot documentation, so if you can point me to some thorough instructions for setting this up, that will be worth some points. Here's some stats:
PostFix MTA using the basic, default configuration, modified only slightly for my particular domain/virtual domain. Ports 25, 110, 143 have been opened on the local firewall, and those ports are being forwarded to the server. Mail clients (Outlook, Outlook Express, and GoldMine 4) will be on the local intranet for the most part, but remote POP/IMAP access will be a necessary function of the server not too far down the road.