Office 11.4.0 update squashes nasty Entourage data loss bug

Among the security patches delivered with Microsoft's 11.4.0 update to Office 2004 this week, there was a fix for a subtle and deeply irritating bug that's been nipping at Exchange users for a long time. Under certain rare circumstances, Entourage users could unexpectedly and unexplainedly lose days or weeks worth of email, poof! I've personally seen this happen a handful of times over the past three years, and it's always a challenging conversation when the affected user asks "What the hell happened?" and the official reply is "Um... let me check the backups for you, mmmkay?"

TUAW reader Vermyndax, who worked with Microsoft support to track down the bug, blogged about the cause and resolution of the issue today:

The bug occurs due to a bad logic assumption. Entourage 2004 treats its local database as authoritative to the mail stored in your mailbox. As such, if the Exchange server happens to be virus-scanning your mailbox when you synchronize your mail, Exchange will refuse to allow Entourage access to the items being scanned. Since Entourage receives no information on the existence of those items, it will mark them for deletion in its local database.

On the next sync, you lose all of those items in the mailbox too. In cases we noted, users were losing large swaths of email at once (on the order of 2-3 weeks' worth all at once).

Yech. While you could recover the mail from Outlook/OWA "Deleted Items," it was a pain — and worse if you didn't notice the problem until after your retention deadline had passed. Upgrading to 11.4.0, assuming you aren't quite ready to make the leap to Office 2008, is sounding better all the time.

Thanks Vermyndax!