First of all you need Windows Server. NT or XP will not do you any good. Exchange Server runs on top of a Windows Server. I think by Windows Domain they meant environment. Like the server i just mentioned. Of course you will need a domain name etc. Only Exchange 2003 with SP2 does push. I'm pretty sure you'll need Windows Server 2003 as well. Not sure on that last one. At any rate what you want to do is very complicated and very expensive. A much easier route would be to pay for a hosted exchange service. There are a lot of them around.
 [BlackJack]