Converting an Exchange Userbase to Unix?

Jwfulcher asks: "This is kind of backwards from what normal people do, which is why i'm having problems finding any documentation on it, but I have around 150 users on exchange, with distribution lists and a few custom recipients as well. The CEO wants to switch to a Unix based POP/IMAP mail solution for licensing reasons (we don't use the groupware functions anyway), I was wondering if anyone knew of a method to convert the exchange userbase and add the users on a FreeBSD system and possibly point to our Radius server (which is capable of doing NT authentication) for authentication on those accounts."

Well..

[cmowire]

I'm not speaking from experience here, but here's a suggestion:

You can open an IMAP server in Outlook and open your Exchange server at the same time and just drag the mail across. For 150 people, you might need a little help to do this, but with a few helpers, it's not totally insurmountable.