How to fix Outlook 'Cannot start Microsoft Outlook. Cannot open the Outlook window' error

Summary

This guide helps you troubleshoot and resolve: How to fix Outlook 'Cannot start Microsoft Outlook. Cannot open the Outlook window' error. Follow the steps below to fix the issue.

Common Causes

If Outlook refuses to start and displays the error “Cannot start Microsoft Outlook. Cannot open the Outlook window”, it usually means Outlook’s navigation pane settings have become corrupted, an Outlook data file is damaged, or the current Outlook profile is no longer valid. This guide walks you through several proven fixes, starting with the quickest and least disruptive options.

Quick Fix Steps

Try these in order. Most users find that one of the first two methods resolves the error immediately.

1. Restart your computer. This clears temporary memory issues that can prevent Outlook from launching.
2. Start Outlook in Safe Mode. Hold the Ctrl key and double-click the Outlook icon, or press Windows + R, type outlook.exe /safe, and press Enter. If Outlook opens in Safe Mode, close it and restart normally.
3. Run Outlook as administrator. Right-click the Outlook icon and select Run as administrator. If this works, the issue is related to user permissions.

Detailed Instructions

Method 1: Reset the Navigation Pane

The navigation pane stores the layout of your folders, calendar, contacts, and tasks. A corrupted navigation pane file is the most common cause of this error.

1. Close Outlook completely.
2. Press Windows + R to open the Run dialog.
3. Type outlook.exe /resetnavpane and press Enter.
4. Outlook will launch and rebuild the navigation pane from scratch.
5. Check if the error is resolved. If not, continue to Method 2.

Method 2: Repair Outlook Data Files

If your Outlook data file (.pst or .ost) is damaged, Outlook may fail to open its window. Use the built-in Inbox Repair Tool to scan and repair the file.

1. Close Outlook.
2. Open File Explorer and navigate to one of the following locations, depending on your Outlook version:
   • C:\Program Files\Microsoft Office\root\Office16\
   • C:\Program Files (x86)\Microsoft Office\root\Office16\
   • C:\Program Files\Microsoft Office\Office16\
3. Double-click SCANPST.EXE to launch the Inbox Repair Tool.
4. Click Browse and select your Outlook data file. The default location is C:\Users\[YourUsername]\AppData\Local\Microsoft\Outlook\.
5. Click Start to scan the file.
6. If errors are found, click Repair.
7. Restart Outlook and test.

Method 3: Disable Problematic Add-ins

A faulty add-in can prevent Outlook from opening its main window. Disable all add-ins and re-enable them one by one to identify the culprit.

1. Close Outlook.
2. Press Windows + R, type outlook.exe /safe, and press Enter.
3. In Safe Mode, go to File > Options > Add-ins.
4. At the bottom of the window, select COM Add-ins from the Manage dropdown and click Go.
5. Clear the checkbox next to each add-in and click OK.
6. Close Outlook and restart it normally.
7. If Outlook opens, re-enable add-ins one at a time, restarting Outlook after each, until the problematic add-in is identified.
8. Keep the faulty add-in disabled or update it through the vendor’s website.

Method 4: Create a New Outlook Profile

If none of the above methods work, your Outlook profile may be corrupted. Creating a new profile gives you a clean configuration while keeping your data intact.

1. Close Outlook.
2. Open the Control Panel and switch the view to Small icons.
3. Click Mail (Microsoft Outlook).
4. Click Show Profiles.
5. Click Add to create a new profile.
6. Enter a name for the new profile (for example, “Outlook New”) and click OK.
7. Follow the prompts to add your email account. For setup instructions, see Setting Up an Email Account in Outlook (POP/IMAP/Exchange).
8. Once the account is configured, select Always use this profile and choose the new profile from the dropdown.
9. Click OK and restart Outlook.

Troubleshooting

Outlook Still Won’t Open After All Methods

• Repair Office installation. Go to Control Panel > Programs and Features, select your Microsoft Office or Microsoft 365 installation, and click Change. Choose Quick Repair first, then Online Repair if the issue persists.
• Check for Windows updates. Go to Settings > Windows Update and install any pending updates.
• Update Outlook. Open any Office application, go to File > Account > Update Options > Update Now.
• Check for conflicting software. Antivirus or firewall programs can occasionally block Outlook. Temporarily disable them to test, then add Outlook to their exclusion lists if necessary.

Error Returns After a Few Days

If the error reappears, the underlying cause may be a recurring add-in conflict or a data file that continues to be corrupted. Re-run the Inbox Repair Tool and review recently installed add-ins or software updates. If the problem persists, Open a Ticket and our support team will assist.

Related Articles

• Troubleshooting Outlook Send/Receive Errors
• Backing Up and Restoring Outlook Data Files (.pst/.ost)
• Setting Up an Email Account in Outlook (POP/IMAP/Exchange)
• Organizing Emails with Rules and Alerts in Outlook
• Using Outlook Calendar and Scheduling Meetings
• Managing Email Signatures in Outlook

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