Excellent
Exchange is an excellent email server program. Running on Windows 2000 Server with all the service packs applied, it performs only as good as how its managed. The sever must have a VSAPI capable anti-virus and anti-spam software. Managing Exchange requires more than average network administrator skills and a good deal of knowledge of Active Directory. Additionally, Outlook clients can benefit from customizations and email anywhere via Outlook Web Access.

No competition.
This is by far the best mail server available on the market - the Active Directory integration alone makes this worth the upgrade from Exchange 5.5. The Outlook Web Client, storage scalability and other enhancements make administration a lot easier for me, and keep my clients happy.

Excellent piece of server software in every respect.

sure beats os x
this mail server is great! i love the web based interface for remote email retrieval

Great Enhancements
This is one of the most compelete product transformations I have seen. Exchange 2000 makes the jump from a mail backbone to a complete collaborative environment for your enterprise. Most notable features include integrated web access, scalable storage, integration with ActiveDirectory for minimal administration. A remarkable product.