Outlook in Crisis: How to Fix the January 2026 Update Freezing Your Inbox

A recent Microsoft January update (KB5074109) is causing Outlook Classic to experience severe performance issues—including freezes, latency, and missing messages in Sent Items—particularly when handling POP3 accounts, PST files, or archiving to OneDrive. Microsoft has no immediate fix and recommends using Outlook on the web or the WebView2-based client; affected users can uninstall the update and reboot to restore Outlook Classic functionality.