Users relying on the classic Outlook application are experiencing a frustrating set of issues following the installation of Windows 11’s latest update, KB5074109. The patch, released in January, has triggered crashes, unresponsive behavior, and even data loss risks when Outlook attempts to access files stored in cloud-based storage like OneDrive or Dropbox.
The problem manifests as Outlook becoming completely unresponsive—freezing with a 'Not Responding' status—and requiring manual termination via Task Manager or a full system restart. Beyond functionality, users report sent emails vanishing from the Sent Items folder and previously downloaded messages being re-downloaded, compounding the disruption.
Microsoft has confirmed the issue affects multiple Windows versions, including Windows 11 (25H2, 24H2, 23H2), Windows 10 (22H2 and LTSC variants), and Windows Server editions (2025, 23H2, 2022, 2019). The company is actively developing a permanent fix, but in the meantime, affected users have two immediate options to regain stability.
The most straightforward solution involves relocating PST files away from OneDrive or other cloud storage services. Storing these files locally should eliminate the freezing behavior and restore normal operation. For users who cannot move files immediately, Microsoft advises using webmail as a temporary alternative, provided their email provider supports it.
Businesses and IT administrators encountering the issue are encouraged to reach out to Microsoft Business Support for urgent assistance. While the workaround is effective, the underlying cause remains unresolved, and users should monitor for an official patch in the coming weeks.
This is not the first time a Windows update has introduced compatibility challenges, but the impact on classic Outlook stands out due to its widespread use in both personal and professional environments. Until Microsoft releases a definitive update, affected users should proceed with caution—particularly when handling critical email data—and consider the suggested workarounds to minimize disruption.
