Exchange 2010 SP1 Rollup 4 has been removed from the Download Center due to an issue where messages from subfolders could get deleted when a parent folder is copied or moved within Outlook. Recovery would still be possible via the “Recoverable Items” folder (Dumpster).
If you have it already installed, you can uninstall it or contact Microsoft Customer Support and request interim update KB2581545 (KB article will be published later). It appears a fixed version of SP1 RU4 won’t be released and instead will be directly superseded by SP1 RU5 scheduled for August.
