Exchange Server 2007 Installation Marathon Day 2 - Why does it only support 64bit OS?

Basically 4GB memory limitation is the bottleneck of 32bit OS. When the hardware become cheaper and cheaper, also users with faster network speed (are you still using dial-up internet?) need faster response from server side.
So in an enterprise environment with thousands clients, 4 GB RAM is much less than neccesary for spooling, scanning virus and filtering spams.

The future of OA under Micorsoft Windows Server and Excahnge Server

"Unified messaging is significant in Exchange 2007 because it is the foundation that
Microsoft will be using to provide unified communications across their entire product
line. Over the next few years, Microsoft will more tightly integrate instant messaging
(IM), voice over IP (VoIP) telephone integration, videoconferencing, data conferencing,
and so forth into a complete, centralized communications system. Today, Microsoft has
several new products they have introduced to the marketplace, including Office
Communications Server 2007, Office Roundtable, and SharePoint 2007, that integrate
technologies together in a unified communications backbone. Exchange 2007 is the first
system that is core to the unified communications strategy that Microsoft is setting
forward because Exchange is the point of connection for email, contacts, remote access,
mobile access, and, now, voice and fax communications."


-- <> Sams