Windows 11 KB5078127 is an 'out-of-band' patch to fix an issue that broke Outlook Classic (POP, PST) after January 2026 Patch ...

Microsoft has issued guidance to uninstall KB5074109 security update or switch to webmail after the patch caused Outlook ...

If your Outlook Classic freezes or hangs when you use POP accounts or deal with PST files, you'll need to remove Windows 11 ...

For how long? Outlook does some housekeeping the the PST/OST file on your computer after you close the client itself. I've seen this take more than a minute in certain rare cases.

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