Update Rollup 23 for Exchange 2007 Service Pack 3 is now available for direct download. This is the last update rollup for Exchange 2007 and support for Exchange 2007 will expire on April 4, 2017.
Aside from all previous updates released since Exchange 2007 SP3, this update also includes new time zone updates.
View: Description of Update Rollup 23 for Exchange Server 2007 Service Pack 3
Download: Update Rollup 23 for Exchange Server 2007 SP3 (KB4011325)