Microsoft is working on a fix for a bug introduced in its June update for Outlook that produces an error message warning of a damaged file that means Outlook needs to close.
Microsoft has confirmed complaints this week from Outlook users who are seeing the message but struggle to repair the email client using the recommended Inbox Repair Tool.
The issue is affecting systems that updated to Version 2005 Build 12827.20268 or higher for Microsoft 365 Apps.
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After starting Outlook users see the error prompt: "Something is wrong with one of your data files and Outlook needs to close. Outlook might be able to fix your file. Click OK to run the Inbox Repair Tool."
But users on Microsoft's Answers forum say the repair tool doesn't fix the problem that Outlook offers to solve, leaving them in the same predicament as when they started.
According to Windows expert Woody Leonard, the repair tool doesn't work because it's attempting to fix a PST file that's completely fine. He also says the bug is actually caused by the June cumulative updates for Windows 10 and that the issue doesn't appear to affect Outlook with OST files.
However, one Outlook user reports getting the error on Outlook with OST files. "Outlook stopped working and said the .ost file was corrupt. Every time I start outlook it offers to repair the ost – but this does not work and outlook does not start," said the user.
Microsoft hasn't determined whether a fix will come via an Outlook update or a Windows update.
"An initial client fix is available in Insider Beta version 13004.10000," says Microsoft. "The Outlook Team is investigating this issue with the Windows Team. We are not sure yet if the primary fix will come from Outlook or Windows. When we have more information on fix details we will add them here."
In the meantime, Microsoft's workaround involves using Registry Edit to force Outlook to ignore the PST file it wrongly classifies as corrupt. However, Microsoft cautions that "serious problems might occur if you modify the registry incorrectly".