Hey Petey,
Unfortunatly, you'll have to have an MTA running to receive the mail, even if you don't want it to send. I'd suggest using sendmail as your mta, but that's just because its what I usually use. You will also have to configure you mta for virtual hosting capabilities. As far as your users, they just have to have a sytem login.
That's virtual mail hosting in a very very small nutshell, it should give you a few places to start on google.
If you still are in need of help feel free to PM me, or catch me on AIM at Sevaa Assistance, I'm always glad to help someone when I can.
If you're looking for fewer headaches, be sure to check out the free hosting offer at
http://www.chiefdelphi.com/forums/sh...ad.php?t=24872, you could always use that for the mail hosting by just point your mx records to that server.
-Randy