Exchange 2007 SP1 RU4

As you know a earlier released build of RU4 slipped onto Microsoft Update and was pulled, see the Exchange blog for more information.
http://msexchangeteam.com/archive/2008/09/11/449787.aspx

Now the real RU4 has been released today but will only be listed on the Windows Download site and not on the Microsoft Update servers.

Update Rollup 4 for Exchange Server 2007 Service Pack 1 (KB952580)
http://www.microsoft.com/downloads/details.aspx?FamilyID=8b492ed2-ea92-412f-a852-3aa1c58d9499&DisplayLang=en

The below links outlines all the changes in the rollup
http://support.microsoft.com/?kbid=952580