KB5074109 “completely useless” Outlook

Last week, Microsoft released the first 2026 updates via Patch Tuesday to Windows 11 with versions KB5074109 and KB5073455. At the same time, the company also released related dynamic updates with versions KB5074108, KB5074208, and KB5073454.

Unfortunately for users, Patch Tuesday introduced two major issues and thus, Microsoft was forced to release emergency OOB updates to fix these issues with versions KB5077744 and KB5077797.

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However, Microsoft also confirmed problems with classic Outlook, as many users claim that the new Windows 11 25H2 and 24H2 update, KB5074109, made the application “completely unusable,” as there are crashes and freezes, unsaved emails, and more.

In a post about the issue, a user, John W, wrote: “Outlook classic is completely useless with this forced Windows update. Random crashes, emails not saving, etc. Hours of troubleshooting to no avail… Uninstalling update KB5074109 fixed the problem for me! Now I can close Outlook smoothly, reopen it, and all progress is saved.”

The post was originally started by Chris Seagrave who also reports that uninstalling the update solved the problem.

Microsoft is of course aware of the problem and states:

“After updating Windows 11 with KB5074109 on January 13, 2026, users with Outlook POP account profiles are reporting that Outlook is not shutting down properly. This means that Outlook will not restart after you close it. Additionally, some users are reporting issues with Outlook crashing or freezing.”

Microsoft says there may be more bugs that haven't been reported yet and that it's currently investigating the issue. For now, uninstalling KB5074109 appears to be the only solution.

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George is still wondering what he is doing here….