Classic outlook freezes upon loading

For classic Outlook freezing during startup, use these steps in order:

1. Check for a hidden dialog box.
   • Press Alt+Tab and look for any Outlook prompt waiting for confirmation.
   • If a dialog box is open, respond to it first. Outlook can appear frozen until that prompt is closed.
2. Wait a few minutes if Outlook is processing something large.
   • Check the Outlook status bar at the bottom.
   • If it is working on a large send/receive, moving many messages, auto-archive, or a large attachment, wait two to three minutes.
3. Start Outlook in safe mode.
   • Press Windows + R.
   • Type outlook.exe /safe and select OK.
   • If Outlook opens, the issue is likely caused by an add-in.
4. Disable COM add-ins if safe mode works.
   • In Outlook, go to File > Options > Add-ins.
   • Select COM Add-ins and then Go.
   • Clear all check boxes to disable the add-ins, then select OK.
   • Restart Outlook normally.
   • If Outlook works, re-enable add-ins one at a time, restarting Outlook after each one, to find the add-in causing the freeze.
   • Do not use Remove during this test. Disable only.
5. Install the latest Windows and Microsoft 365/Office updates.
   • Out-of-date files can cause Outlook to stop responding.
   • Install both Windows updates and Office updates, then restart the PC.
6. Repair Office.
   • Close all Microsoft 365 apps.
   • Open Control Panel > Programs and Features.
   • Right-click Microsoft Office and select Change.
   • Start with Quick Repair. If that does not help, use Online Repair.
7. Repair Outlook data files.
   • Run the Inbox Repair Tool (scanpst.exe) to scan and repair .pst or .ost files.
   • Corrupted Outlook data files can cause startup freezes.
8. Create a new Outlook profile.
   • Close Outlook.
   • Open Control Panel > Mail > Show Profiles.
   • Select Add and create a new profile.
   • Set Outlook to prompt for a profile, then start Outlook and choose the new profile.
   • If Outlook works with the new profile, the original profile is likely corrupted.
9. Run the Classic Outlook Advanced Diagnostics troubleshooter.
   • It can automatically check common causes such as add-ins, damaged Office files, oversized mailboxes, corrupted data files, antivirus conflicts, and profile issues.
   • It works for classic Outlook on Windows 10 or later.

References:

• Classic Outlook not responding, stuck at "Processing," stopped working, or freezes
• Outlook for Windows not responding, hangs, freezes, or stops working
• Outlook not responding error or Outlook freezes when you open a file or send mail