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Deprecating «Outlook must close» error related to incorrect cumulative Windows update

Deprecating "Outlook must close" error related to incorrect cumulative Windows update

Internal conflict seems to be a recurring theme at Microsoft, but this is taking it to new levels. Someone forgot to test the latest fixed version of Outlook with the latest corrected version of Windows. The result is an error message that makes Outlook not work.

The official announcement appears in Microsoft 365 support site :

After upgrading to version 2005 Build 12827.20268 or later and starting Outlook, you may see the following error message:

The Outlook team is investigating this issue with the Windows team. We are still not sure if the main solution will come from Outlook or Windows. When we have more information about the repair details, we will add them here.


If you click OK, the ScanPST Inbox Repair Tool begins. Go through the repair process, restart and surprise! – the error message reappears. Rinse to wash. Repeat. It is not known how many hours were lost this weekend. However, the good news is that your PST file is fine and has always been.

  • Use PST files, not OST files;
  • Run Microsoft 365 version 2005 Current Channel, version 12827.20268 (as of June 2) or Current Channel, version 12827.20336 (as of June 9);
  • And you installed the June 2020 cumulative update for Win10 (KB 4557957 for version 2004, KB 4560960 for version 1903 or 1909, or KB 4561608 for version 1809).

The Microsoft solution, published in that Microsoft 365 support article, involves manually editing the registry so that Outlook ignores the fake «corrupt» PST file at startup. In fact, the «corrupt» PST file is not corrupt at all. It’s just that Windows is messing with Outlook.

If you do not want to touch your register, Diane Poremsky in Slipstick has an easy to download solution.

The internal report that we would say is that the error is actually in the cumulative updates from June, but that it will be easier for Microsoft to fix the problem by fixing it in a new version of the current Microsoft 365 channel.

We hope that the people at Office are not particularly happy about this.

Tell me one more time … who’s testing these things?

Convenience for Outlook developers beat available at Lounge .