Microsoft urges users to uninstall a Windows 11 update after Outlook becomes unresponsive

Microsoft has issued a critical warning for Windows 11 users after confirming that update KB5074109 can cause Outlook Classic profiles with POP accounts and PST files to hang or become unresponsive. Affected users are experiencing frequent freezes, unsaved draft emails, and cases where Outlook will not reopen unless the process is ended in Task Manager or the PC is restarted, particularly after the January 13, 2026 update.

As a temporary measure, Microsoft recommends uninstalling KB5074109 to restore Outlook functionality. Users can remove it via Settings, then Windows Update, Update history, Uninstall updates, select KB5074109, and confirm. Microsoft cautions that uninstalling the patch also removes more than 100 security fixes included in the January 2026 update.

The company says there is no simple in app workaround right now and recommends using webmail or moving PST files out of OneDrive until a fix is available, but says other workarounds can be complicated. The update is also linked to apps becoming unresponsive or throwing errors when opening or saving files to cloud backed storage like OneDrive or Dropbox. In some Outlook setups, PSTs stored on OneDrive can cause Outlook to stop responding, require a restart or Task Manager to recover, and sent emails may not appear in Sent Items. Microsoft says it is still investigating and has not published a permanent fix beyond removing KB5074109.