Service Pack 3 is now available to download for the Microsoft Exchange Server 2007. With this service pack now we can install Exchange Server 2007 on the Windows Server 2008 R2.
We can download Exchange 2007 SP3 here.
For an overview of the new features that are available in Exchange Server 2007 SP3, see "What's New in Exchange Server 2007 SP3".
Additionally, Exchange 2007 SP3 includes all the updates that are included in Update Rollup 4 and earlier for Exchange 2007 SP2. For more information, see Microsoft Knowledge Base article 981383, Description of Update Rollup 4 for Exchange Server 2007 Service Pack 2.
For a list of schema changes that are made by Exchange 2007 SP3, see Active Directory Schema Changes (SP3).