A recent Windows update, designated KB5074109, is causing significant disruptions for Outlook users, potentially freezing the application and leading to frustrating data inconsistencies.
The core of the problem lies in how Outlook interacts with cloud storage services like OneDrive and Dropbox. When PST files – where Outlook stores your emails – reside within these cloud folders, the application can become unresponsive, effectively locking up.
Users are reporting a disturbing pattern: Outlook simply hangs, displaying a dreaded “Not Responding” message. Attempts to reopen the program often fail, forcing a hard shutdown through the Task Manager or a complete system restart.
The consequences extend beyond mere inconvenience. Sent emails mysteriously vanish from the Sent Items folder, and Outlook begins redownloading messages you’ve already received, consuming bandwidth and time.
This issue isn’t limited to a single version of Windows. It impacts a wide range of systems, including Windows 11 (versions 25H2, 24H2, and 23H2), Windows 10 (version 22H2, Enterprise LTSC 2021, and 2019), and various Windows Server editions.
The problem is particularly acute for those using POP email accounts or any Outlook profile where PST files are stored directly on OneDrive. The update, released on January 13, 2026, seems to trigger a conflict between Outlook and the cloud storage synchronization process.
While Microsoft is actively developing a patch, a temporary solution is currently recommended: access your email through webmail if your provider supports it. This bypasses the problematic Outlook application altogether.
For those who must continue using the desktop application, the most effective workaround involves relocating your PST files *off* of OneDrive and onto a local drive. This breaks the connection causing the instability.
Microsoft advises contacting the application developer for alternative file access methods, but for Outlook specifically, moving the PST files is the most direct path to restoring functionality. Businesses facing widespread issues should consider reaching out to Microsoft Business Support for assistance.
This update joins a growing list of reported issues stemming from KB5074109, including problems with system shutdowns, black screen crashes, and File Explorer malfunctions, highlighting the potential for unforeseen consequences with even seemingly routine updates.
