The Exchange team has released an updated version of update rollup 4 for Exchange 2010 SP1 to the Download Center. This updated release is being made available after a complete review and revalidation of the list of fixes included in the previously released version of Rollup 4 dated June 22, 2011.
- Customers who have installed KB 2509910 (Rollup 4, dated June 22, 2011) and KB2581545 (fix for Rollup 4 regression) do not need to install KB 2579150 (re-released Rollup 4) but may do so if they choose to.
- Customers who have already installed KB 2581545 and want to update their systems to the updated Rollup 4 should first uninstall KB 2581545 (or any interim updates) prior to installing the new rollup.
- You do not need to uninstall original RU4 (KB 2509910) to install the re-released RU4 package (KB2579150).
- The re-release of Rollup 4 does not change the release plans for Update Rollup 5 for Exchange Server 2010 Service Pack 1. Rollup 5 is currently scheduled to release in August 2011.
The installation wizard clearly says that it is Update Rollup 4-v2
Download the v2 Update Rollup 4 for 2010 SP1 here
More info @ source