Just a bit of an update for everyone here. I know things are taking way longer than I'd originally projected, and for that I apologize. Anyway, finally got to spend some good, solid hours working on configuring the mail and DNS servers. I'm switching to a completely new mailserver (courier) and it's taking me a while to even learn what all the options are, much less pick the ones I need, and get them all playing nicely. I have made some good progress though, and the mailserver bit seems to be functional. I can send and recieve email, login with IMAP, and pretty much everything else. There should be a host of new features going with this, including full SSL support on all email, and more comprehensive email options for people with their own domains. You'll now be able to have multiple email boxes (with separate logins/passwords) , mapped to any addresses (on your domain) you want.
On a nerdy-humorous side note, (which most of you won't understand, but that's okay) I spent about 2 hours trying to figure out why in the world the server couldn't talk to itself. That is, I can ping the server from my desktop, and I can ping the desktop from the server, but the server couldn't ping itself. Thought it had something to do with the virtual server context security and such... finally figured out that somewhere along the way, I'd managed to delete the loopback adapter from the default runlevel... meaning the internal network interface was not going. That I didn't realize it a lot sooner is probably one of the stupider things. I guess it's something so low-level, and so 'assumed' that it never occurred to me to check it.
Anyway, things are looking like they're gonna work out well, and once I get everything put together, it's gonna be a lot easier to maintain and organize than the old server. The next task is to integrate spam filtering into courier... Oi! After that, I think I'm just about finished. All that's really left is to rewrite some of the stuff like the account management interface to work with the new system. Then it's just a matter of transferring everyone's accounts and files. I've learned my lesson, and I'm not about to promise a timeframe yet, but I am actually getting somewhere. :-)
Oh, and like I mentioned before, I think I'll be able to switch servers nearly-live, with maybe only an hour or two of downtime. Keep your fingers crossed on that one.