Emergency Windows 11 KB5078127 Update (25H2) Resolves Outlook POP & PST Crashes and Unresponsive Apps Post January 2026 Patch Tuesday

Microsoft Releases Windows 11 KB5078127 Emergency Update

On January 25, 2026, Microsoft has initiated the rollout of Windows 11 update KB5078127, categorized as an ‘out-of-band’ patch. This update addresses significant issues affecting Outlook Classic, particularly for users relying on POP accounts and PST files, as well as other applications that have become unresponsive following the January 2026 Patch Tuesday.

Even if you haven’t encountered problems after the January update, KB5078127 will still be made available to your device. Users will see a notification stating “2026-01 Update (KB5078127) (26200.7628) is available” within the Windows Update settings. For devices running version 24H2, this update will elevate the OS to Windows 11 Build 26100.7628. The downloading process typically takes around five minutes with a download speed of 200 Mbps, followed by approximately three minutes for installation, requiring one reboot.

This is the second emergency update for Windows 11 in a short span of time, with the first one, KB5077744, having been released on January 17, which was optional. In contrast, the latest patch is crucial due to the severity of the identified issues.

2026-01 Update (KB5078127) (26200.7628) is available

Post-installation, Outlook Classic, when used with POP accounts and PST files, should function normally again, along with third-party applications which were experiencing unresponsiveness since the latest Patch Tuesday update.

“In certain Outlook configurations that store PST files on OneDrive, Outlook may hang and fail to reopen unless the process is terminated or the system is restarted. Users may also see missing sent Items or previously downloaded emails being re‑downloaded, ” Microsoft noted.

Microsoft has indicated that this issue also extends to other third-party applications that utilize cloud storage for file management, including OneDrive and Dropbox.

How to Obtain Windows 11 KB5078127

For those seeking direct download links, you can find the options for Windows 11 KB5078127 here: 64-bit and ARM-64 versions.

Understanding Windows 11 KB5078127

Windows 11 KB5078127 is classified as an ‘out-of-band’ emergency update that will download automatically to rectify app responsiveness issues, including those plaguing Outlook Classic. While users experiencing these issues should definitely install the update, it is set to apply automatically.

Our assessments have confirmed that Outlook Classic becomes unresponsive when working with POP accounts and PST files. For instance, users with only Microsoft 365 accounts can open Outlook without issues, but adding a POP account or utilizing PST files leads to Outlook becoming stuck.

Outlook hangs after Windows 11 KB5074109

To regain access to Outlook, users must either terminate the Outlook.exe process through Task Manager or reboot their systems each time they wish to open the application.

This difficulty extends beyond Outlook, reportedly affecting various third-party applications that depend on cloud synchronization.

While Microsoft recommended uninstalling Windows 11 KB5074109 to resolve the Outlook issues, this is not an advisable route due to the critical security fixes encompassed within that update. To mitigate disruptions, Microsoft suggested that users resort to webmail access when Outlook Classic malfunctions.

Compiling Windows Issues Post-January 2026 Update

The update KB5074109 has brought to light several issues. Notably, Remote Desktop connections were hindered, limiting user access. While Microsoft confirmed these problems and provided emergency fixes, the repercussions of the January 2026 release, such as crashes in Outlook Classic and third-party applications, are more pressing.

Although Microsoft has not openly addressed various complaints regarding Sleep mode and File Explorer malfunctioning, the recent KB5078127 update effectively remedies the problems with unresponsive applications.

**Summary of Issues Related to the January 2026 Windows 11 Update** *Source: WindowsLatest.com*
Issue Details	Current Status	Workaround	Affected Windows Versions
Outlook Classic freezes.	Acknowledged by Microsoft	Resolved in out-of-band update (KB5078127)	All supported versions of Windows
Third-party apps become unresponsive.	Acknowledged by Microsoft	Resolved in out-of-band update (KB5078127)	All supported versions of Windows
Black screen or wallpaper resets.	Not officially acknowledged	Restart Windows or reapply wallpaper manually	Windows 11 25H2, 24H2
Sleep mode (S3) stops working on older PCs.	Not officially acknowledged	No reliable workaround available	Windows 11 24H2 / 25H2 on systems using S3 sleep
Desktop.ini broken in File Explorer.	Not officially acknowledged	No workaround; folders still function but UI is incorrect	Windows 11 25H2, 24H2
Citrix Remote Desktop not working.	Acknowledged by Citrix	Remove the update or switch to alternatives	Windows 11 25H2, 24H2 and Windows Server 2025, 2022
Remote Desktop connectivity issues.	Acknowledged by Microsoft	Resolved in first out-of-band update (KB5077744)	All supported versions of Windows
Shutdown functionality fails.	Acknowledged by Microsoft	Resolved with first out-of-band update (KB5077797)	23H2
System fails to boot.	Acknowledged by Microsoft	Use Windows Recovery or reinstall Windows using an ISO	25H2 and 24H2