Good, cheap/free replacement for Exchange 5.5?
Hello fellow geeks. I need help picking a good, cheap/free Exchange server alternative for a client. He's running ES 5.5 right now, on an old POS NT4 SP6 box, and only using it for email (no shared folders, calendar, etc), so it makes little sense to upgrade to the latest and greatest when all the client needs is email.
The NT4 box will probably remain in service, acting as a domain controller (upgrading to Server 2003 with enough licenses is overkill, and $$$$$$), and the new mail exchange software will run on a new, modern Dell server with XP Pro. If there's an alternative to the Small Business Server 4.5 that's running on the NT box, that'd be a nice bonus. Ideally, the NT4 box (hardware) would run a compact version of Linux, handling the domain, email, filtering, internal website, and/or VPN.
I've found a few interesting options, some completely free, some costing nearly as much as Exchange 2003 itself, but I'd like to hear your opinions.