Getting We're sorry, but outlook has run into an error that is preventing it from working correctly. Outlook will need to be closed as a result. Would you like us to repair now?

Start classic Outlook in Safe Mode first; if it opens successfully, disable its COM add-ins and re-enable them individually to identify the one causing the startup failure.^1^

1. Test Outlook without add-ins

1. Close Outlook.
2. Press Windows key + R.
3. Enter:

outlook.exe /safe

4. Select OK, accept the default Outlook profile, and enter your password if requested.

If Outlook opens:

1. Go to File → Options → Add-ins.
2. At the bottom, select COM Add-ins under Manage, then select Go.
3. Record or screenshot the enabled add-ins.
4. Clear every checkbox and select OK. Disable them—do not use Remove.
5. Exit Outlook and reopen it normally.
6. If the error is gone, re-enable one add-in at a time, restarting Outlook after each one. Leave the add-in that reproduces the error disabled.^1^

2. Check the recent POP/PST Windows-update issue, if applicable

If this is a POP account using a PST file and the problem began after the January 13, 2026 Windows updates, install the latest available Windows updates because Microsoft reports that this known issue was addressed in newer builds:

1. Open Settings → Windows Update.
2. Select Check for updates.
3. Install all available current updates.
4. Restart Windows and test Outlook.^2^

Do not uninstall security updates unless the affected update has been specifically identified. Removing updates reduces protection, and organization-managed devices should be handled by the IT administrator.

3. If Safe Mode also fails

Run Microsoft’s startup troubleshooter:

1. Open the Windows Get Help app.
2. Search for the classic Outlook startup troubleshooter.
3. Follow its prompts.

It requires Windows 10 or later, must run on the computer containing classic Outlook, and does not apply to new Outlook.^3^

Next, test a new Outlook profile:

1. Follow Microsoft’s Create an Outlook profile procedure linked from the startup guidance.
2. Close Outlook.
3. Hold Shift while starting Outlook.
4. In Choose Profile, select the new profile and choose OK.

If the new profile works, the original profile is damaged. Back up any local PST data before removing the old profile because removing a profile deletes its offline cached content.^1^

4. Repair Microsoft 365 or Office

If Outlook still fails, perform Online Repair, which repairs the entire Office suite:

• Windows 11: Right-click Start → Installed apps → Microsoft 365 or Office → … → Modify → Online Repair → Repair.
• Windows 10: Right-click Start → Apps and Features → Microsoft 365 or Office → Modify → Online Repair → Repair.

Restart the computer after completion. Online Repair is more comprehensive than Quick Repair and may require an internet connection.^4^

If Online Repair itself fails, note its error code and contact the organization’s Microsoft 365 administrator or support team; that indicates an Office installation problem rather than enough evidence to identify an Outlook add-in or profile issue.

References

1. I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window” | Microsoft Support
2. Outlook (Classic) error - Microsoft Q&A
3. Classic Outlook troubleshooters | Microsoft Support
4. Repair an Office application