How to fix Microsoft Outlook not opening or running after a Windows update

Summary

This guide helps you troubleshoot and resolve: How to fix Microsoft Outlook not opening or running after a Windows update. Follow the steps below to fix the issue.

Common Causes

After a Windows update, Microsoft Outlook can occasionally fail to launch, freeze on the splash screen, or crash shortly after opening. These problems are usually caused by corrupted app data, an incompatible add-in, or a damaged Outlook profile. The steps below will walk you through resolving the issue, starting with the quickest fixes and moving on to more thorough solutions if needed.

Before You Begin

• Make sure your computer is fully updated. Open Settings > Windows Update and select Check for updates. Install any pending updates, then restart your PC.
• Confirm the issue is specific to Outlook by trying to open another Office app such as Word or Excel.
• If you use Outlook with a Microsoft 365 business account, ensure your licence is still active at account.microsoft.com/services.

Quick Fix Steps

1. Restart your computer fully (do not just shut the lid or sign out).
2. Open Outlook in Safe Mode by pressing Win + R, typing outlook.exe /safe, and pressing Enter. If Outlook opens in Safe Mode, an add-in is the likely cause.
3. If Outlook opens in Safe Mode, disable add-ins one at a time via File > Options > Add-ins > Manage: COM Add-ins > Go.
4. If Outlook still will not open, proceed to the detailed instructions below.

Detailed Instructions

Repair the Outlook Desktop App

1. Close Outlook completely. Check Task Manager (Ctrl + Shift + Esc) and end any OUTLOOK.EXE processes.
2. Open Settings > Apps > Installed apps (Windows 11) or Apps & features (Windows 10).
3. Locate Microsoft Outlook or Microsoft 365 in the list and click Modify.
4. Select Online Repair and click Repair. This performs a thorough fix and may take several minutes.
5. Restart your computer when prompted and try opening Outlook again.

Reset the Outlook Profile

1. Press Win + R, type outlook.exe /profiles, and press Enter.
2. In the Mail dialog box, click Show Profiles.
3. Select your default profile and choose Copy to back it up, then give the copy a recognisable name such as Outlook_Profile_Backup.
4. Select the original profile, click Remove, then create a new profile with the same name and add your email account again.
5. Restart Outlook and re-enter your account credentials if prompted.

Clear the Outlook App Data Cache

1. Close Outlook and ensure no OUTLOOK.EXE processes are running in Task Manager.
2. Press Win + R, type %localappdata%\Microsoft\Outlook\RoamCache, and press Enter.
3. Select all files in the folder (Ctrl + A) and delete them. Do not delete the folder itself.
4. Repeat with %localappdata%\Microsoft\Outlook, deleting any temporary .ost files for accounts that are no longer in use.
5. Restart Outlook. Your mailbox will resynchronise from the server.

Check for Conflicting Windows Updates

1. Open Settings > Windows Update > Update history.
2. Note the most recent update installed just before Outlook stopped working.
3. Return to Windows Update and select Uninstall updates.
4. Choose the suspect update and click Uninstall. Restart your PC.
5. Once Outlook is working again, pause updates for up to five weeks via Windows Update > Pause updates while Microsoft releases a fix.

Reinstall Microsoft 365 as a Last Resort

1. Open Settings > Apps > Installed apps and uninstall Microsoft 365 or Microsoft Office.
2. Restart your computer.
3. Visit aka.ms/office-install from the affected PC and sign in with the account tied to your licence.
4. Click Install Office and run the installer.
5. Open Outlook and re-add your email account. For setup guidance, see Setting Up an Email Account in Outlook (POP/IMAP/Exchange).

Troubleshooting

Outlook Crashes Immediately After Opening

This usually points to a corrupt .ost file or a faulty add-in. Start Outlook in Safe Mode (outlook.exe /safe). If it opens, disable add-ins under File > Options > Add-ins. If the issue persists, delete the .ost file for the affected account in %localappdata%\Microsoft\Outlook and let Outlook rebuild it.

Outlook Hangs on the Loading Profile Screen

Reset the profile using the steps above. If the problem continues, create a fresh profile in the Mail dialog box and add your account again. For data recovery, refer to Backing Up and Restoring Outlook Data Files (.pst/.ost).

Outlook Will Not Send or Receive After Repair

After an Office repair, account passwords sometimes need to be re-entered. Go to File > Account Settings > Account Settings, select the affected account, click Change, and re-enter your password. For ongoing send/receive errors, see Troubleshooting Outlook Send/Receive Errors.

Outlook Opens but Displays "Cannot Start Microsoft Outlook" Error

This message typically indicates a corrupted profile or damaged Navigation Pane settings. Delete the RoamCache folder contents and reset the profile as described above. If the error remains, rename the file Outlook.xml located in %appdata%\Microsoft\Outlook to Outlook.xml.old and restart Outlook.

Calendar or Rules Not Working After the Fix

Repairing or reinstalling Office can occasionally clear local rules. Recreate any missing rules using File > Manage Rules & Alerts. For guidance, see Organising Emails with Rules and Alerts in Outlook. Calendar items should resynchronise automatically, but you can verify them under Using Outlook Calendar and Scheduling Meetings.

Preventing Future Issues

• Keep both Windows and Office updated to the latest versions to benefit from stability fixes.
• Only install trusted Outlook add-ins from verified publishers, and review them periodically.
• Avoid shutting down your computer during Outlook updates or while the app is syncing.
• Back up your Outlook profile and important data files (.pst) regularly.
• If a Windows update causes issues, pause updates temporarily and check Microsoft's known issues page before installing new patches.

Still Having Issues?