Microsoft: Windows 11 update causes Outlook freezes for POP users

Microsoft is investigating widespread reports that a January Windows 11 security update is causing the classic Outlook desktop client to freeze and hang for users with POP email accounts.

POP (Post Office Protocol) is an email retrieval protocol used for downloading emails from a server to a local device. While POP isn't as widely used as IMAP or Exchange, it is still popular among home users and small businesses.

This known issue affects users who have installed the KB5074109 security update for Windows 11 25H2 and 24H2, with those impacted reporting that classic Outlook does not exit properly and will not restart after being closed.

"This is an emerging issue, and we don't have all the symptoms yet, but we will update the topic as we understand the issue better," Microsoft said in a Thursday support document.

Microsoft's Outlook and Windows teams are investigating the problem, but the company has yet to provide a timeline for a fix or workaround.

Microsoft said that it will update its advisory as investigators learn more about the scope and cause of this known issue.

Until a permanent fix is released to address this bug, affected users can work around it by uninstalling the KB5074109 update by opening the Settings app, going to Windows Update > Update history > Uninstall updates, and clicking the "Uninstall" link next to "Security Update for Microsoft Windows (KB5074109)."

"As soon as the January 14th update was issued, Outlook started freezing and crashing. I uninstalled KB5074109 and now Outlook works fine again," one of the affected users said.

"No repairs or fixes listed worked except uninstalling the security update. I had to postpone updates to keep it from reinstalling."

However, it's important to note that, just as Microsoft also warns, removing security updates may leave Windows devices exposed to malware and other threats, since they patch vulnerabilities that are often already being exploited in attacks.

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Posted Saturday 17 January 2026 at 5:24 am AEST (my time).

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