There are various issues caused by the security updates for Windows released on January 13, 2026. Among other things, issues with Outlook Classic when retrieving POP mail or program freezes have been reported. On January 24, 2026, Microsoft released out-of-band updates for affected Windows versions to fix the problem. I've discussed the details in this article [use the translate option in the side bar of my German blog to read the article in English or other languages].
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We hit this in our environment right after the January 13, 2026 Patch Tuesday updates. Classic Outlook would hang or freeze, and the common pattern was PST files stored in OneDrive or Dropbox, plus some POP profiles. The short-term workaround was moving the PST back to local storage or uninstalling KB5074109 and pausing updates, but that is obviously not ideal from a security standpoint.
Applying Microsoft's January 24 out-of-band fixes resolved it for us on the affected Windows 11 builds. For anyone managing WSUS or Intune rings, it is worth validating the OOB KB for your specific Windows version before broad deployment, then pushing it to a pilot group first.