Why can i not open my Outlook email

Start classic Outlook in Safe Mode first; whether it remains open determines the correct next step.

1. Test Outlook in Safe Mode

1. Press Windows key + R.
2. Enter:

      outlook.exe /safe
   

3. Select OK.
4. If Choose Profile appears, accept the default profile and select OK.

Safe Mode starts Outlook without COM add-ins, which helps identify whether an add-in is likely preventing a normal launch.^1^

If Outlook stays open in Safe Mode

1. Go to File → Options → Add-ins.
2. At the bottom, select COM Add-ins under Manage, then select Go.
3. Take a screenshot of the enabled add-ins.
4. Clear every checkbox—do not use Remove.
5. Close and reopen Outlook normally.
6. If it now opens, enable add-ins one at a time, restarting Outlook after each one. Leave the add-in that causes the crash disabled.

2. Check these specific update-related conditions

Microsoft 365 Insider builds

If enrolled in Microsoft 365 Insider, open another Office application such as Word and check File → Account → About Word.

If the version is 16.0.19113.20000 or 16.0.19115.20000, use File → Account → Update Options → Update Now and update to build 16.0.19119.20000 or later. Microsoft documents the launch crash in those two builds as fixed in 16.0.19119.20000.^2^

If Outlook also closes in Safe Mode

Check for Microsoft’s documented ucrtbase.dll crash before using the rules-cleanup command:

1. Right-click Start → Event Viewer.
2. Open Windows Logs → Application.
3. Find an Outlook crash with Event ID 1000 or 1001.
4. Treat it as the documented issue only if the details match:
   • Outlook Version 2407, build 17830.20138 or higher
   • Faulting module: ucrtbase.dll
   • Exception code: 0xc0000005
   • Fault Bucket: 1620625936954482602, Type 4

If those details match, corrupted or unprocessable server-based rules are the documented condition.^3^

Warning: The following command removes both client-side and server-side Outlook rules. Record important rules through Outlook on the web first, if possible.

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

      Outlook.exe /cleanrules
   

4. Select OK.

If the event details do not fully match, skip /cleanrules and continue below.

3. Reset the navigation pane

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

      Outlook.exe /resetnavpane
   

This removes navigation-pane customizations without deleting email.^1^

4. Create a fresh Outlook profile

1. Close Outlook.
2. Open Control Panel.
3. Search for and open Mail (Microsoft Outlook).
4. Select Show Profiles → Add.
5. Enter a profile name and complete the account setup.
6. Select Prompt for a profile to be used, then start Outlook and choose the new profile.

If Outlook opens with the new profile, the original profile is damaged. Do not remove the old profile until any locally stored data has been backed up.^1^

5. Repair Office or run the troubleshooter

If the new profile also fails:

1. Open Settings → Apps → Installed apps.
2. Find Microsoft 365 or Microsoft Office.
3. Select … → Modify → Quick Repair.
4. If that does not work, repeat and choose Online Repair. Online Repair is more extensive and may require signing back into Office.^4^

On Windows 10 or later, the Get Help application also provides a classic Outlook startup troubleshooter for startup and profile problems.^5^

References

1. I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window” | Microsoft Support
2. Certain users enrolled in the Microsoft 365 Insiders Program cannot launch classic Outlook for Windows | Microsoft Support
3. Classic Outlook unexpectedly closes at start up on faulting module ucrtbase.dll | Microsoft Support
4. [Classic Outlook](https://support.microsoft.com/outlook/getstarted/outlook-for-windows-not-responding-hangs-freezes-or-stops-working)
5. Resolve Outlook for Windows issues with automated troubleshooting tools | Microsoft Support