Fixed: the January 2026 Windows bug that hung classic Outlook

This is an explainer about an older Windows bug, not a new one. Classic Outlook profiles with POP mail or PST data files hung after Windows updates released Jan. 13, 2026, Microsoft says. The company has since marked the problem as fixed. Its known-issue page on the bug was last updated Feb. 3, 2026, according to Microsoft.

[BleepingComputer reported that Microsoft looked into complaints about a Windows 11 security patch from January that made the classic Outlook desktop app lock up for people who get mail through POP accounts.](https://www.bleepingcomputer.com/news/microsoft/microsoft-windows-11-update-causes-outlook-freezes-for-pop-users/) For anyone whose Outlook still acts up after updating, Microsoft has published repair steps and tells users to keep running Windows Update until it reports "You're up to date."

Key facts

• BleepingComputer reported the bug hit people who installed KB5074109 on Windows 11 25H2 and 24H2.
• Microsoft says the Jan. 13, 2026, Windows updates caused classic Outlook to hang for profiles that rely on POP mail or PST data files.
• Microsoft's list of affected versions also names Windows 11 23H2 and Windows 10 22H2.
• Microsoft lists the January bug as fixed through Windows itself.
• If sync trouble continues, Microsoft advises fixing the POP profile and running Scanpst.exe on the PST file.

Background

Once the Jan. 13, 2026, Windows updates were installed, classic Outlook setups relying on POP mail or PST data hung and failed to close the right way, Microsoft says. The company adds that the problem may show up in any profile that keeps its PST files on OneDrive.

People hit by the bug told BleepingComputer that classic Outlook would not shut down cleanly and would not start again once closed. BleepingComputer said the affected update was KB5074109, a security patch for Windows 11 versions 25H2 and 24H2.

Microsoft's own page names a wider group of systems: Windows 10 version 22H2, along with Windows 11 in its 23H2, 24H2 and 25H2 versions. How many people ran into the problem has not been made public.

Microsoft also spelled out the warning signs. Its list includes Outlook showing "Not Responding" and refusing to reopen unless its process is ended in Task Manager or the PC is restarted. Microsoft says sent messages could also go missing from the Sent Items folder, and some mail could download a second time.

BleepingComputer describes POP as an email retrieval method that pulls messages from a server down to a local device. The outlet says many small businesses and home users still rely on it.

What it means for you

If you use classic Outlook with a POP account, or keep PST files on OneDrive, the fix comes through Windows Update. Microsoft says to keep checking for updates until Windows says the PC is fully current.

Before the fix, some users got Outlook working again by removing KB5074109, BleepingComputer reported. The path runs through Settings, then Windows Update, then Update history and finally Uninstall updates. That trade-off carried a cost. According to BleepingComputer, Microsoft cautions that taking security updates off a Windows PC may expose it to malware and other threats.

Before the fix, Microsoft offered two stopgaps: reading mail in a web browser through webmail, and taking PST files off OneDrive. If you made either change, you can decide whether to keep it once your PC is current.

Practical steps

1. Open Windows Update, install everything it offers and repeat until it shows no more updates are needed.
2. If mail still does not sync, fix your POP Outlook profile, as Microsoft advises.
3. If some folders will not open, use Microsoft's Scanpst.exe utility to fix the PST file.
4. If problems linger, Microsoft's earlier stopgaps were webmail and shifting PST files off OneDrive.

What happens next

Microsoft lists the issue as resolved, and the most recent update to its known-issue page came on Feb. 3, 2026, according to the page. Users who still see freezes after updating are pointed to the profile and PST repair steps rather than to a new patch.

Whether any newer Windows update is causing fresh Outlook crashes is not known from the sources for this story.

FAQ

What caused classic Outlook to freeze? BleepingComputer tied the freezes to KB5074109, a January security update for Windows 11. Microsoft describes the trigger as the Windows updates released Jan. 13, 2026.

Which setups were hit? Microsoft says the bug hit classic Outlook setups that use POP mail or PST data, and it could reach any profile that keeps PST files on OneDrive.

Which versions of Windows were affected? Microsoft's list covers Windows 11 in versions 23H2, 24H2 and 25H2, as well as Windows 10 version 22H2.

Is the bug fixed? Yes. Microsoft lists it as resolved and tells users to keep running Windows Update until the PC is current.

What if Outlook still hangs after updating? Microsoft's advice is to fix the POP profile first, then run Scanpst.exe if some folders cannot be opened.

Is removing the update a good idea? BleepingComputer reported that Microsoft cautions against it, since a PC without security updates may be exposed to malware.