1.5 Exchange Server 2010 SP1 and Active Directory

As far as Active Directory is concerned, its minimum level needs to be on a Windows Server 2003 level, both for the domain functional level and for the forest functional level. This might be confusing, since Exchange Server 2010 only runs on Windows Server 2008 or Windows Server 2008 R2, but that's just the actual server which Exchange Server 2010 SP1 is running on!

The Schema Master in the forest needs to be Windows Server 2003 SP2 server (Standard or Enterprise Edition) or higher. Likewise, in each Active Directory site where Exchange Server 2010 SP1 will be installed, there must be at least one Standard or Enterprise Windows Server 2003 SP2 (or higher) server configured as a Global Catalog server.