Microsoft released Exchange 2010 SP3 RU8 yesterday alongside Exchange 2013 CU7 and a slew of other updates, including MS14-075 security fixes. Today they have pulled the Exchange 2010 SP3 RU8 update because of a regressive bug discovered in the RPC client access layer.
Update 12 December: Microsoft has released V2 of Exchange 2010 SP3 RU8 to address the issue discovered earlier this week.
The bug first came to light after customers deployed Exchange 2010 SP3 RU8 and discovered that Outlook clients could no longer work with items in mailboxes. Outlook would connect, but any attempt to open an item resulted in a “cannot open item” error.
Unsurprisingly given that the bug is in the MAPI RPC layer, clients that use other protocols such as ActiveSync (EAS), Outlook Web App, BlackBerry, and even IMAP4/POP3 all continued to work. Somewhat confusingly, some users reported that Outlook worked just fine or that clients started to work after a while.
Microsoft has identified where the problem lies and is working on a fix. I’d expect to see it in the near future. In the meantime, if you have deployed Exchange 2010 SP3 RU8 you should consider removing it from servers and revert to Exchange 2010 SP3 RU7.
The bug does not affect Exchange 2007 SP3 RU15 or Exchange 2013 CU7. Exchange 2013 uses a different connectivity model and the offending component is not present in Exchange 2007.
And of course, this issue proves once again the wisdom of testing all updates before putting them into production. Fools rush in where savvy administrators test.
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