Microsoft Outlook is a powerful email client that offers many useful features for messaging and calendaring. However, it is prone to various issues and errors. The ""Cannot start Microsoft Outlook. Cannot open the Outlook window" is one such error that Outlook users face while using the application. This error prevents the users from using the application, accessing their emails, and sending/receiving new messages. The error can occur due to different reasons. Below, we will be explaining the possible reasons behind the ""Cannot start Microsoft Outlook. Cannot open the Outlook window" error and some effective solutions to resolve it.
Reasons for ""Cannot start Microsoft Outlook. Cannot open the Outlook window" Error
There are several reasons that may trigger this error in Microsoft Outlook. These include:
- Corrupt or damaged Outlook profile
- Corrupt Outlook PST file
- Incompatible or faulty add-ins
- Conflict with security software, such as antivirus
- Damaged Navigation Pane
- Compatibility mode is on for Outlook
- Damaged or corrupt Outlook installation or program files
- Large or oversized PST file
- Outdated Outlook client
- Faulty Windows updates
- Insufficient system resources
- Permission related issues
Methods to Fix the ""Cannot Start Microsoft Outlook. Cannot open the Outlook window" Error
Follow the given methods to resolve the 'Cannot start Microsoft Outlook' error.
1. Update Outlook
Installing the latest Outlook updates brings fixes and patches to the bugs in the program that might be causing the 'Cannot open the Outlook window' error. To update Outlook, go to File > Office Account > Office Update > Update Options (Update now).
Outlook will check for new updates and start an update wizard, and automatically download the latest updates and install them.
If the update option is unavailable or disabled in your Outlook, you can update it manually by downloading and installing the latest build from the Microsoft site.
2. Check and Disable Compatibility Mode
Running Outlook in Compatibility Mode can also cause such issues. Therefore, make sure that Compatibility Mode is turned off for Microsoft Outlook. The steps are as follows:
- Right-click the Outlook shortcut and select Properties.
- Click on the Compatibility tab and then uncheck Run this program in compatibility mode for.
- Once done, click Apply > OK.
- Then, Restart Outlook.
3. Use the Microsoft Support and Recovery Assistant
Microsoft Support and Recovery Assistant is a free tool from Microsoft that helps Outlook users troubleshoot problems with their Outlook client. When you run the tool, it performs a few tests to find what's wrong with your Outlook client, system, or Outlook data file. Then, it provides the solutions to fix the issue. The steps to use this tool are as follows:
- Download and install Microsoft Support and Recovery Assistant.
- After installation, launch the program and click 'I agree.'
- Select Outlook from the options and click 'Next.'
- Select Outlook Won't Start or Other problems and click 'Next.'
- Click 'Yes' and then click 'Next.'
- Complete the wizard and apply the suggested solutions.
4. Run Outlook in Safe Mode
Outlook add-ins help enhance the user experience as they offer certain features that don't exist in the base application. Sometimes, these add-ins interfere with Outlook. As a result, you may encounter the 'Cannot open the Outlook window' error. You can run Outlook in safe mode to confirm if the problem is caused by add-ins. Follow these steps:
- Launch the Run tool by pressing the Windows + R keys.
- Enter Outlook.exe /safe in the input field and press the OK button.
- Select your Outlook profile and click OK. Outlook will open in safe mode.
If you can use Outlook without any issues in the safe mode, then it confirms that the Outlook won't open issue is caused by add-ins. You can disable the add-ins to fix the problem. To do so, follow these steps:
- Go to File > Options > Add-ins.
- In the Manage menu, select COM Add-ins and click the Go button.
- In the COM Add-ins window that opens, unselect all the add-ins and click OK.
- Restart Outlook and check if the ""Cannot start Microsoft Outlook" issue is resolved.
5. Reduce Outlook Data File Size
If your Outlook data file (PST) has become large-sized, then it can create problems with your Outlook. If you're facing the 'Cannot open Outlook window' error, you can check and reduce the size of your data file. To reduce the PST file size, you can compact the file or archive old emails. Here's how:
Compact the PST File
Empty the Deleted Items folder and delete unimportant emails and other mailbox items. When mail items are deleted, they leave whitespace in the PST file. You can compact the PST file to remove this whitespace and further reduce the PST file size. The steps are as follows:
- In Outlook, go to File > Info > Account Settings > Account Settings.
- Click on the Data Files tab.
- Choose your PST file and click Settings.
- Then, click Compact Now under the General tab.
Archive Old Mail Items
By archiving old mail items (moving old mail items to a new local PST file), you can significantly reduce the PST file size. The steps to archive mail items in Outlook are as follows:
- In Outlook, click File > Info > Tools > Clean up old items.
- Then, select the Archive this folder and all subfolders option and choose the folder you want to archive.
- Make sure to choose or enter a date under Archive items older than.
- Finally, click Browse to choose a location where you would like to save the archived mail items in a PST file and click OK.
Repeat these steps to create more local archives of your mail items and reduce the PST file size. You can also split the Outlook data file manually or by using a third-party PST splitter tool.
6. Remove XML Files
Corrupt XML files in the Outlook directory can also be a reason why you cannot start Microsoft Outlook. You can remove these files to fix the problem. To do that, follow these steps:
- Press the Windows + R keys to launch the Run utility.
- Type AppData in the input field and press Enter.
- In the AppData folder that opens, go to Local > Microsoft > Outlook.
- Open the Outlook folder as per your Outlook version.
- Remove the XML files from the folder and restart Outlook.
7. Reset Navigation Pane
Outlook allows the users to customize the navigation pane which is the leftmost pane in the main window. Sometimes, customizations in the navigation pane can prevent you from starting Outlook. You can reset the navigation pane to fix the problem. Follow these steps:
- Close Outlook and other applications that are using Outlook.
- Press the Windows + R keys to launch the Run tool.
- In the Run window, type ""outlook.exe /resetnavpane" and press Enter.
8. Repair or Reinstall Microsoft Outlook
Corrupt or damaged Outlook or MS Office program files may prevent the application from working properly and lead to errors. In such a case, repair the MS Outlook installation by following these steps:
- Click the Start menu or Windows button on the keyboard and then click on the Settings icon or type Settings in the search bar.
- Select Apps & features.
- Find and right-click on the Microsoft Office application. You will see two options ? Modify and Uninstall. Choose the Modify option.
- Select the Quick Repair option and then click on Repair. When the process is complete, it will display a notification on the screen.
- If you're still having problem after Quick Repair, you can choose the Online Repair option.
- When you click on Repair, the wizard will display a message before proceeding with the repair process. Read the message carefully and click on the Repair button again.
- Wait for the repair process to finish. It will be like a fresh installation and may take some time, depending on your internet connection speed and the severity of the issue.
- When the process is complete, restart your system.
If repairing MS Outlook (MS Office) does not work, you can reinstall the MS Office. For this, you need to uninstall the MS Office. After uninstalling, download the latest build and install it on your system.
9. Repair Outlook Data File (PST)
Certain events can corrupt or damage Outlook data files. These events include abrupt system shutdown, power failure, malware infection, etc. If your file is corrupted, then Outlook may throw the ""Cannot start Microsoft Outlook" error. You can repair the file to resolve the error.
You can repair the Personal Storage Table (PST) file by using the Inbox Repair Tool (ScanPST.exe). The ScanPST is located in Outlook's installation directory. Run ScanPST.exe and provide the path to the PST file. Then, click the Start button to repair the file.
Inbox Repair Tool is effective in fixing minor corruption in Outlook data files. In case the corruption is severe, then you need to use an advanced PST repair tool, such as Stellar Repair for Outlook.
Stellar Repair for Outlook is a powerful PST repair tool that offers the following features:
- Repairs severely corrupt and large-sized Outlook data files
- Recovers complete PST mailbox data, including emails, contacts, attachments, tasks, calendars, etc.
- Splits and compacts Outlook data files (Technician edition)
- Directly exports the repaired PST to the Office 365 account (Technician edition)
- Previews repaired mailbox before saving
- Saves repaired Outlook data file in different file formats - PST, EML, RTF, HTML, PDF, and MSG
Conclusion
The error ""Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened." can prevent you from accessing your mailbox. However, you can easily fix this error by applying the methods mentioned in this post. If the error is caused by a corrupt PST file, then you can use ScanPST or a third-party Outlook PST repair tool, such as Stellar Repair for Outlook to repair the data file and fix the problem. The third-party tool can help restore all the mail items from severely corrupt, large-sized, or encrypted PST files to new PST file. It also provides an option to export all mail items directly to the live Exchange Server or Microsoft 365 in a few clicks.