rosoft’s January 2026 Windows 11 update (KB5074109) has caused headaches for users of the classic Outlook email client — leaving many desktops unable to properly open Outlook, lose sent items, or freeze unexpectedly. In response, Microsoft has provided temporary workarounds while it develops a permanent fix.
📉 What Went Wrong With the Update?
The Windows 11 KB5074109 patch — released on January 13, 2026 — was intended to improve system security and stability. Unfortunately, the update triggered a bug that disrupts how the classic Outlook app interacts with email data files, especially PST files stored in cloud services such as OneDrive or Dropbox.
Users affected by the bug report that:
- Outlook freezes or becomes unresponsive and shows “Not Responding.”
- Outlook fails to restart unless its background process is manually terminated.
- Sent emails do not appear in the Sent Items folder, even though they were successfully sent.
- Outlook may redownload previously downloaded mail, disrupting workflows.
These issues have affected not just Windows 11 (across multiple versions), but also some Windows 10 and Windows Server platforms.
🧰 Microsoft’s Workaround Solutions
While Microsoft works on an official patch, the company recommends the following temporary fixes for affected users:
✅ Move PST Files Out of OneDrive
If Outlook’s data files (PSTs) are stored on OneDrive or another cloud-backed location, moving them to local storage often resolves the freeze issues.
🌐 Use Webmail Instead
Access your email via webmail — a reliable alternative that avoids the local Outlook client bug.
🧑💼 Contact Microsoft Business Support
For enterprise environments or urgent support needs, Microsoft recommends reaching out to official business support channels for dedicated help.
❗ Note: Some workarounds — like uninstalling the update — may be complex or may expose systems to other security risks if the patch is removed. Make sure to consult IT administrators before taking those actions.
🔄 Outlook Users Weigh In
IT professionals and end users have taken to discussion forums to share their experiences — with some noting similar freezing behavior and suggesting rollback or local file adjustments as interim fixes.
🧠 What’s Next?
Microsoft is actively working on a permanent fix for the classic Outlook issue and will release it as part of a future Windows update.
Until then, affected users should consider using webmail, moving PST storage off cloud services, or consulting support teams if their workflow depends on classic Outlook.