Fix Outlook Startup Error: Cannot Open the Outlook Window - How to Fix Windows Defender Permission Denied Error-Outlook Hangs on Startup After Windows 10 Update

Updated 2026-06-14 02:38:19security-tools
Fix Outlook Startup Error: Cannot Open the Outlook Window - How to Fix Windows Defender Permission Denied Error-Outlook Hangs on Startup After Windows 10 Update
Before changing system settings, save your work and note the exact error text so you can compare results after each step.

Extra verification checklist

  • Restart the affected app after changing permissions or configuration files.
  • Test the same workflow in a clean browser profile or a temporary user account.
  • Compare the result on another network if the error may be connection related.