The Outlook Freeze: New Windows 11 Update Breaks POP3 Accounts in Outlook Classic

Microsoft’s January 2026 security release KB5074109 appears to be the catalyst for instability in Outlook Classic when used with the latest Windows 11 24H2 or 25H2 updates, with users reporting the client freezing or a prolonged white screen after adding POP/SMTP accounts. The issue is limited to POP3 configurations, as IMAP users are not affected, and the application often stalls about five to ten minutes after launch, sometimes failing to exit gracefully or reinitialise on subsequent attempts.

The primary Outlook process can linger in the background, and forceful termination may only provide a temporary window before the cycle repeats. Microsoft has officially acknowledged the anomaly, but a formal workaround has not yet been disseminated; for the time being, the most effective recourse described is the uninstallation of the KB5074109 update, followed by a temporary suspension of system updates to restore stability for Outlook Classic.

This guidance follows a wave of user feedback in the Feedback Hub and CVE Watchtower references linked in the report, which was published on 19 January 2026.