- if you have already deployed Exchange 2007 SP1, then use Rollup 1 for SP1, and here is the link for it to Read more about this new Rollup and to download it:
Description of Update Rollup 1 for Microsoft Exchange Server 2007 Service Pack 1
- If you are still on Exchange 2007 RTM Version, then use Rollup 6 for Exchange 2007 RTM, from this link :
Description of Update Rollup 6 for Exchange Server 2007
Note, before you update your Production Exchange SP1 or RTM Version, you have to test the update process on the lab, which is the recommendation always from everybody. so start testing it, and update your production servers to the latest updates and rollups for RTM and SP1 Versions.
Another thing, If you don't upgrade your RTM Version to SP1, then you missed the whole fun :) SP1 has a great features and new technologies as well as the latest rollup updates for SP1 which are 5 (Rollup Update # 6 came after the release of SP1 so its not included in this version of Service Pack, it might be included in the newer release of Service Pack 2, I don't know really :) )