POP -> IMAP w/ Maildirs?

["Keith G. Murphy" <keithmur@mindspring.com>]

I have an application in mind where I download some folks' POP3 mail
from their ISPs to our local server, then present their E-mail (they're
Win95 users on our local network) using an IMAP server.

So far I can do everything very simply using fetchmail + procmail -d +
UW IMAP.

However, I'd like to go to a solution, probably using maildirs, that
does not involve messages in their home directories; in fact, maybe not
requiring them to have accounts on our Linux server at all.

I've been digging into the procmail documentation, and trying to figure
out how to use maildirs in UW IMAP, but I've got the feeling someone out
there has already done this.

Any simple methods for this?

TIA.