The Exchange Server 2007 SP3 is now available for download. This third service pack for Exchange 2007 enables Exchange 2007 to be installed on the Windows Server 2008 R2 version of the operating system. It has been quite some time that the people are waiting for a new update so that the exchange can be installed on Windows Server 2008 R2, so MS worked quickly to deliver SP3 in order to meet this requirement 

Download Exchange 2007 SP3 here. Clean installations of SP3 on a new server is possible by using this download.

Microsoft has also released the Exchange 2010 SP1 Beta; you can click here to know more.