Microsoft Outlook is a powerful email client that offers many useful features for information management. However, Outlook users occasionally run into problems with the application. For instance, the ""Cannot start Microsoft Outlook. Cannot open the Outlook window" error is one of the prevalent errors that Outlook users face. This error prevents Outlook users from using the application.
How to Fix ""Cannot Start Microsoft Outlook" Error?
Try the following methods to resolve the 'cannot start Microsoft Outlook' error:
1. Run Outlook in Safe Mode
Outlook add-ins help in enhancing 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' issue.
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 Windows + R keys.
- Enter Outlook /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 are able to 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 that, follow these steps:
- Go to File > Options > Add-ins.
- In the Manage menu, select COM Add-ins and click the Go button.
- Select your Outlook profile and click OK. Outlook will open in safe mode.
If you are able to 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 that, 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.
2. Reduce Outlook Data File Size
Outlook creates two types of data files on the local system - PST (for POP3 email accounts) and OST (for MAPI/IMAP accounts). If your Outlook data file has become large-sized, then it can create problems with your Outlook.
If you're facing the 'can't open Outlook window' issue, you can try reducing the size of your data file. You can do that in different ways. For instance, you can:
- Split Outlook data file manually or by using a third-party PST splitter tool.
- Empty the Deleted Items folder and remove unimportant emails and other mailbox items.
- Compact the data file manually.
- Archive old emails in a new Outlook data file.
3. Update Outlook
Sometimes, installing the latest Outlook updates can help fix the 'cannot open the Outlook window' issue. To do that, go to File > Office Account > Office Update > Update Options (Update now).
4. Remove XML Files
Corrupt XML files in 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 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. For instance, Outlook 2016 has the folder named 16.
- Remove the XML files from the folder and restart Outlook.
5. 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 Windows + R keys to launch the Run tool.
- In the Run window, type ""outlook.exe /resetnavpane" and press ENTER.
6. Repair Outlook Data Files
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 Microsoft's Personal Storage Table (PST) file by using Inbox Repair Tool (ScanPST.exe). The ScanPST is located in Outlook's installation directory. After locating the utility, 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, including emails, contacts, attachments, tasks, calendars, etc.
- Splits and compacts Outlook data files (Technician edition)
- Directly exports the repaired PST to 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." is one of the most problematic Outlook errors. It's because this error prevents you from accessing your mailbox. That said, 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 Repair Tool to repair the data file and fix the problem.