I'll give this a shot. Any solution that doesn't maintain at least the current client-side status of emails (ie, requires redownload, or new account on client) is a complete nonstarter, though.
Justin> Maybe I'm misunderstanding - all of our clients use pop3
Justin> (thunderbird and eudora). Do pop3 and imap overlap somehow, or
Justin> does the server use IMAP internally regardless of the client
Justin> protocol settings?
No, IMAP and POP are just the transport mechanisms. But POP is old
and doesn't keep state well. If you can, upgrade all your clients to
IMAP, thunderbird will be easy to do so, and I suspect Eudora will be
as well, but I haven't touched it in years.
why don't you just setup a test IMAP account and try a client?