Microsoft has released Update Rollup 6 for Exchange Server 2007

Update Rollup 6 for Exchange Server 2007 resolves issues that were found in Exchange Server 2007 since the software was released. This update rollup is highly recommended for all Exchange Server 2007 customers.

For a list of changes that are included in this update rollup, see KB942846.

This is a cumulative update rollup and replaces the following:

KB930809 Update Rollup 1 for Exchange Server 2007 (KB930809)
KB935490 Update Rollup 2 for Exchange Server 2007 (KB935490)
KB935999 Update Rollup 3 for Exchange Server 2007 (KB935999)
KB940006 Update Rollup 4 for Exchange Server 2007 (KB940006)
KB941421 Update Rollup 5 for Exchange Server 2007 (KB941421)

This update rollup does not apply to Exchange Server 2007 Service Pack (SP1). For a list of update rollups applicable to Exchange Server 2007 SP1, refer to the section Update rollups for Exchange Server 2007 Service Pack 1 in the Knowledge Base article KB937052.

Update Rollup 6 for Exchange Server 2007 (KB942846)