Outlook 365 freezes. Cannot open emails or folders

Follow these steps in order until Outlook stops freezing. Test Outlook after each step.

1. Install the latest Office and Windows updates

• Outlook works best when fully updated.
• Install updates as described in Install Office updates.
• Restart the PC and try Outlook again.

2. Start Outlook in Safe Mode and disable add-ins Add-ins are a common cause of freezing.
3. Close Outlook.
4. Press Windows + R, type: Outlook /safe and select OK.
5. If Outlook runs without freezing:
   • Go to File > Options > Add-Ins.
   • At the bottom, next to Manage, choose COM Add-ins and select Go.
   • Clear all check boxes to disable all add-ins, then select OK.
   • Restart Outlook normally.
6. If Outlook now works, re-enable add-ins one by one, restarting Outlook each time, until the problematic add-in is found and left disabled.
7. Repair Office If Outlook still freezes, repair the Office installation.
8. Close all Office apps.
9. Open Control Panel.
10. Select Programs and Features (or Uninstall a program).
11. Find the Microsoft 365/Office installation, right-click it, and select Change.
12. Choose Online Repair (or Repair) and complete the process.
13. Restart the PC and test Outlook.
14. Repair Outlook data files (.pst/.ost) Corrupt data files can cause freezing.
15. Close Outlook.
16. Use the Inbox Repair Tool (SCANSPST.EXE) as described in Repair Outlook Data Files (.pst and .ost).
17. After the repair completes, reopen Outlook and test.
18. Create a new Outlook profile If the profile is damaged, creating a new one can resolve freezing.
19. Close Outlook.
20. Open Control Panel > User Accounts > Mail.
21. Select Show Profiles.
22. Select the existing profile and choose Remove (ensure data is backed up or stored on the server before removing).
23. Select Add.
24. Enter a Profile Name.
25. Enter the user name and primary email address, then select Next and complete setup.
26. Start Outlook with the new profile and test opening folders and emails.
27. Check antivirus and other integrations Antivirus or other integrations (for example, Skype for Business/Lync) can affect Outlook performance.

• If antivirus has Outlook integration or Outlook add-ins, temporarily disable that integration or add-in within the antivirus software (be aware this can reduce protection; consult the antivirus vendor for safe configuration).
• If Skype for Business/Lync is integrated with Outlook, disable the integration:
  1. Open Lync/Skype for Business.
  2. Select the gear icon > Tools > Options.
  3. Select Personal and clear the check boxes in Personal information manager.
  4. Select OK, then restart Outlook and Lync.

If Outlook still freezes after all these steps, run the Classic Outlook Advanced Diagnostics troubleshooter (for classic Outlook on Windows 10 or later) as described in the Outlook performance article, and follow the guidance it provides.

References:

• Outlook not responding error or Outlook freezes when you open a file or send mail
• Outlook performance is slow in the Microsoft 365 environment
• Outlook not responding, stuck at "Processing," stopped working, or freezes
• Outlook crashes or stops responding when used with Office 365