Small Business Server does have Exchange in it. Just make sure that the version you get has Exchange 2003.
As a standalone, Exchange 2003 is the way to go. It's a dot upgrade from 2000, so it's Exchange 6.5. It has a number of improvements over Exchange 2000, and Microsoft is not expected to do any major upgrades for a number of years, meaning you can settle into it and ride this version a long way.
Restoring files from Exchange 2000 is a real bitch, and Exchange 2003 makes that much easier. And it works much better with Active Directory if you have that than did 2000.
It also optimizes when you use it with Outlook 2003. How, I'm not exactly sure yet, I'm still playing with my new exchange server myself Learn more here
Yes - in your environment Stand-Alone Exchange 2003 is absolutely the way to go!
The main reason is that HK is totally correct above.
The second reason is that Small Business Server has to be the Domain Server as well... So you'd affectively be building a whole new domain which would then require migrating users over, etc... Not the most fun job in the IT admin world...
Couple of things to remember:
Exchange 2003 SHOULD be run on Windows 2003 Server... I've read where it can be run on Windows 2000 Server but I highly advise against it.
Exchange 2003 should NOT be run on the First Domain Controller (i.e. the one with the FSMO roles).
Make sure and read up on the installation instructions as there are several steps to perform PRIOR to actually installing Exchange.
I've rolled out Exchange 2k and Exchange 2003 - I LOVE the changes in 2003, love how its Web Access works, and really am pleased with the upgrades in Outlook 2003 (which btw you get a free license for every user you by Exchange for, and it comes on CD with Exchange)...
Let me know if you have any more questions...
PM me or look for me on the Folding Forums... I seem to haunt there the most...
Are you Folding for a cure? Why not? Its easy, free, and doesn't hurt anyone - in fact it can only help!