The newest Exchange Server, which is 64-bit only, is before year-end. 

The 2010 version of Exchange is being touted as a hybrid -- equally at home as the foundation for a hosted e-mail service or a corporate messaging infrastructure.

Microsoft already hosts more than 5 million users on Exchange 2010 as part of its Live@Edu program.

Michael Atalla, group product manager for Exchange, announced the release on the Exchange Team blog and called out a number of new features: support on the 64-bit versions of Windows Server 2008 and 2008 R2; support for in-place upgrades from the Exchange 2010 RC to the 2010 RTM; and co-existence with Exchange 2007 and 2003 servers.