I can’t start Microsoft Outlook or receive the error “Cannot start Microsoft Outlook. Cannot open the Outlook Window”

Use the classic Outlook startup troubleshooter to diagnose and fix several common classic Outlook for Windows issues for you.

1. Select the button below to start the classic Outlook startup troubleshooter.

   Start

2. Click Open if you get a pop-up window indicating This site is trying to open Get Help.

3. Follow the prompts in the Get Help window.

If the troubleshooter can't fix your issue, or if you'd like to fix it yourself, see the next section.

Sometimes add-ins can conflict with Outlook. Starting Outlook in safe mode, which starts Outlook without add-ins loaded, can tell you if an add-in is the source of the problem.

Start Outlook in safe mode

1. Press the Windows key + R to open the Windows Run dialog. (It will likely appear near the lower left of your screen.)

2. In the Open box, type Outlook /safe, then choose OK.

3. In the Choose Profiles dialog box, accept the default setting of Outlook and choose OK.

   

4. If prompted, enter your password and choose Accept.

If Outlook is able to start in safe mode, then the problem is likely with one of your add-ins. You'll need to disable all of your add-ins before restarting Outlook, as described in the following procedures:

If Outlook is NOT able to start in safe mode, then try the next proposed solution below, entitled Create a new Outlook profile. 

Disable add-ins

1. In the upper-left corner of Outlook, choose File > Options > Add-ins.

2. At the bottom of the View and manage Office Add-ins, make sure the Manage box shows COM Add-ins, and then choose Go.

3. As a precaution, when the COM Add-ins listing of your current add-ins opens, do one of the following:

   • Manually record the title of every selected add-in listed under Available Add-ins.

     or

   • Take a screenshot of the property sheet and save the image to a location of your choice.

4. After you've captured the titles of the selected add-ins, clear all selected check boxes, and then choose OK.

   Caution: Click a check box to clear it. Don't select an add-in and choose Remove. If you have administrator rights, you could actually delete the add-in. For this troubleshooting exercise, you want to disable, not delete, an add-in.

5. Choose File > Exit.

Restart

1. Press the Windows key + R to open the Run dialog.

2. In the Open box, type Outlook.

   Note: If the program loads properly, it's likely that one of your add-ins is the source of the error and you need to identify which one. To determine which add-in is the problem, enable one add-in at a time.

3. In the upper-left corner of Outlook, choose File > Options > Add-ins.

4. Select the check box next to an add-in you want to re-enable, and then choose OK.

5. Repeat all steps until you've re-enabled all of the original add-ins and revealed the source of the error.

   Important: Remember, if Outlook opens in safe mode, you've revealed the add-in you just enabled as a source of the error.

   • Restart Outlook again and disable the add-in you enabled that produced the problem, and then start Outlook.

   • Make sure you go through the restart-disable-restart process for every add-in that was originally enabled in Outlook. An error could be caused by more than one add-in.

Your profile contains your Outlook settings. Occasionally, that profile can become corrupted. You can determine if it's corrupted by creating a new profile and changing which profile is used when Outlook starts.

1. To open the Control Panel, do one of the following:

   • For Windows Vista or Windows 7, select the Windows Start > Control Panel.

   • For Windows 8, Windows 10, or Windows 11, select the Windows Start button, type control panel in the Search box, then select the Control Panel app. 

     Note: For Windows 10 and 11, in Control Panel, make sure the View by box in the upper-right corner is set to Category.

2. For Windows 11, select User Accounts.

3. Choose Mail.

4. In the Mail Setup - Outlook dialog box, choose Show Profiles > Add.

   

5. In the Profile Name box, type the name you want to use for your new profile.

   

6. On the Auto Account Setup page for the Add Account Wizard, under E-mail Account, fill in Your Name, E-mail Address, and Password, and then choose Next.

   

   Note: The Add Account Wizard automatically searches for your mail server settings.

7. Choose Finish and you'll find the new profile name you added listed on the General tab in the Mail dialog box.

8. Under When starting Microsoft Outlook, use this profile, choose Prompt for a profile to be used, and then choose OK.

Use a different profile

1. Restart Outlook.

2. In the drop-down list in the Choose Profile dialog box, choose the new profile name you created.

   

3. Choose OK.

   Note: If Outlook starts normally, then you've identified your Outlook profile as being corrupt and the source of your problem.

Should you decide to remove a profile, back up the data files first. All offline cached content will be deleted when you choose Remove. For more information, see Introduction to Outlook Data Files (.pst and .ost).

Outlook stores all your email messages, meetings and events, contacts, and tasks in data files. These files occasionally might become corrupted. You can run the Inbox Repair Tool (scanpst.exe) to scan your Outlook data files and repair errors.

1. Exit Outlook to use the Inbox Repair Tool.

   Note: The content in the left pane is determined by the Outlook version you're using.

2. Visit the link below for instructions.

   • Repair Outlook Data Files (.pst and .ost)

The navigation pane is the leftmost pane in Outlook where you'll find your folder list and the icons to move between Mail, Calendar, People, and Tasks. Running the /resetnavpane command removes all customizations to the navigation pane.

1. Close Outlook.

2. Press the Windows key + R to open the Run dialog.

3. In the Open box, type Outlook.exe /resetnavpane, and then choose OK.

For more information, see Support for Office 2016 and 2019 clients connecting to Microsoft 365 services has ended.