Citing an issue impacting some customers who have installed "Exchange 2010 SP1 RU4" into their Exchange environment, the Exchange team just announced of removing SP1 RU4 from Download Center -- and recommend customers "DON'T proceed with any planned deployments of SP1 RU4."
Microsoft releases SP1 Rollup 4 on June 22nd this year.
Kevin Allison, GM, Exchange Customer Experience blogged, "A small number of customers have reported when the Outlook client is used to move or copy a folder that subfolders and content for the moved folder are deleted. After investigation we've determined that the folder and item contents don't appear in the destination folder as expected but may be recovered from the Recoverable Items folder (what was previously known as Dumpster in older versions of Exchange) from the original folder. This behavior occurs due to a customer requested change in SP1 RU4 which allowed deleted Public Folders to be recovered. Outlook and Exchange aren't correctly processing the folder move and copy operations causing the folder contents to appear to be deleted."
OWA and Exchange Web Services clients aren't affected by this change and process the folder move or copy actions correctly.
Allison promises "We'll be providing a fix in Exchange 2010 SP1 RU5, scheduled for release in August, which prevents the content loss in the target location during the move/copy process."
"In addition, we're also working with the Outlook development team to examine their code for proper behavior and identify if a fix is necessary from the client."
If you have already deployed SP1 RU4, it's recommend to obtain an Interim Update that resolves this issue -- by contacting Microsoft Customer Support.
[Source: Exchange Team Blog]