Guess I was not understood - Running Microsoft Exchange On a Linux Box - Can it be done?

["Angel Gabriel" <badmangabriel lycos co uk>]

Thank you to the numerous people that mailed me privatly on the list in
response to my question. But I think I've been misunderstood. My previous
post may have been a bit long, so I'll get down to the basic facts about my
network, and what I want to do.

1) People can email just fine.
This is not the problem

2) People use Outlook, Outlook Express, Netscape, all manner of cliets
The client is not the problem

3) I want a uniform back end solution, for the users of Outlook. The people
that need to collaborate online, the ones that are away from the office a
lot, not reachable by phone, onsite, etc etc.

This would mean running MS Exchange. Which is not a problem. I just don't
want to set up a W2K server, 'JUST' to run MS Exchange. So this leaves me
two choices:

A) Attempt to run MS Exchange under wine, or maybe VMware
B) Run a linux based alternative that provides the same functionality, AND
is compatible with Outlook clients.