THE January 2026 update has been found to severely impair the Outlook Classic desktop client, with POP3 configurations and PST data management prone to persistent latency or total freezing, hindering productivity. In some cases, similar unresponsiveness occurs when third‑party apps try to archive files to cloud repositories such as OneDrive, suggesting a potential systemic fault.
According to Microsoft, there is no definitive remediation for the Classic version, and official documentation describes the available workarounds as labyrinthine; users are advised to temporarily migrate to the web‑based interface or the WebView 2‑based Outlook client. For those unwilling to switch, the only remaining recourse is to uninstall the offending update, via the update history in system settings, specifically KB5074109, with a reboot expected to restore Outlook Classic.
Microsoft has also confirmed that this update adversely affects the Sent Items directory, where messages may not appear even after sending and the app may Not Respond. Consequently, those reliant on Outlook Classic are urged to roll back the update immediately, while moderate users can adopt the web alternative as a temporary measure ahead of a forthcoming patch.