Outlook is unexpectedly closing

Dear Mohammed,

Thank you for your update.

To help us proceed with further investigation and pinpoint the root cause of Outlook unexpectedly closing, please kindly share the results of the troubleshooting steps you've performed, particularly focusing on:

• Did Outlook behave differently in Safe Mode or after disabling add-ins?
• What were the outcomes of the Office repair and new profile creation?
• Regarding GWSMO: Did you specifically try running the GWSMO Repair Tool or recreating the GWSMO profile as suggested previously? What were the results?
• Any specific error details from the Windows Event Viewer related to the Outlook crashes?

Please share these test results with us via a private message here in the Microsoft Community. This allows us to review the specific details of your situation securely and helps me to escalate your issue to the technical team for a deeper dive.

To view private email options, sign in to Microsoft Community> use the email account that posted this thread information to Microsoft Community> > click Profile in the upper-right corner, and then select My Profile.  

Your cooperation and detailed information are greatly appreciated as we work to find a solution for you.

Kind regards,

Kai-L - MSFT | Microsoft Community Support Specialist

Dear Kai-L

I’ve tried the steps you suggested, but we are still experiencing the issue. Please note that we are using GWSMO for syncing emails with Outlook.

Dear Mohammed,

Just following up to see if the previous suggestions helped resolve the issue. Let us know how things are going, your update would be greatly appreciated!

Dear Mohammed,

Thank you for posting in Microsoft Community.

I understand that you're facing a critical issue where Outlook is unexpectedly closing continuously while users are working, and upon reopening, they receive the prompt: "Outlook couldn't start last time. Safe Mode can help you troubleshoot the problem... Do you want to start in Safe Mode?" This behavior typically indicates underlying instability, often related to add-ins, corrupted data files, or issues with the Outlook installation itself. Here are some steps to help you troubleshoot and resolve this issue:

1: Test in Safe Mode (Crucial Diagnostic Step)

The prompt itself offers this. If Outlook works stably in Safe Mode, it almost certainly points to an add-in or a customization causing the crash.

1. When you get the "Outlook couldn't start last time..." prompt, click Yes to start in Safe Mode.
2. Work in Safe Mode for a while. If Outlook doesn't crash in Safe Mode, proceed to Step 2 (Disable Add-ins).
3. If Outlook still crashes in Safe Mode, it suggests a deeper issue like a corrupted Outlook profile, data file, or Office installation. Proceed to Step 3 (Repair Office).

2: Disable Add-ins (If Safe Mode Works)

1. Exit Outlook completely.
2. Open Outlook normally (not in Safe Mode). If it crashes quickly, try opening it in Safe Mode again by holding Ctrl while launching Outlook, then click "Yes" when prompted.
3. Once Outlook is open (even if it's in Safe Mode):
   • Go to File > Options.
   • Click on Add-ins in the left-hand pane.
   • At the bottom of the "Add-ins" window, next to "Manage: COM Add-ins," click Go...
   • Uncheck ALL the add-ins listed.
   • Click OK.
4. Restart Outlook normally (close it and open it without holding Ctrl).
5. If Outlook runs stably now, one of the add-ins was the cause. You can then go back to the COM Add-ins list and re-enable them one by one, restarting Outlook after each one, until you identify the problematic add-in. Once found, leave it disabled or look for an update from its vendor.

3: Repair Microsoft Office Installation

1. Close all Office applications, including Outlook.
2. Go to Windows Settings (Windows key + I) > Apps > Apps & features.
3. Scroll down and find your Microsoft Office or Microsoft 365 installation in the list.
4. Click on it, then click Modify (or sometimes "Change").
5. You'll likely be presented with options:
   • Choose Quick Repair first. This is faster and often fixes common issues.
   • If Quick Repair doesn't work, go back and choose Online Repair. This takes longer as it redownloads installation files, but it's more thorough.
6. Follow the on-screen prompts to complete the repair.
7. Restart your computer after the repair is complete.
8. Try opening Outlook normally.

4: Create a New Outlook Profile

Outlook profiles can become corrupted and cause crashes. This creates a clean slate without affecting your existing data files initially.

1. Close Outlook.
2. Open the Control Panel. (You can search for "Control Panel" in the Windows search bar).
3. In the Control Panel, search for Mail (or "Mail (Microsoft Outlook)"), and select it.
4. In the Mail Setup dialog box, click Show Profiles...
5. Click Add... to create a new profile. Give it a distinctive name (e.g., "OutlookTest").
6. Follow the prompts to add your email account(s) to this new profile. Use the exact same settings as your existing account.
7. Once the new profile is set up, in the "Mail Setup" dialog box, under "Always use this profile," select your newly created profile from the dropdown list.
8. Click OK.
9. Open Outlook. If it works stably with the new profile, your old profile was corrupted. You can then import data from your old PST/OST file if necessary (File > Open & Export > Import/Export) or set the new profile as default.

5: Repair Outlook Data Files (PST/OST)

Corrupted PST or OST files can cause crashes.

1. Use the Inbox Repair Tool (Scanpst.exe) to scan and repair your Outlook data files.
2. The tool is located in the Office installation folder; run it and follow the prompts.
3. Click Start to begin the scan. If errors are found, click Repair. You might need to run it multiple times.
4. Once repaired, try opening Outlook normally.

6: Ensure Office is Fully Updated

1. Open Outlook.
2. Go to File > Office Account (or "Account").
3. Under "Product Information," click Update Options > Update Now.
4. Allow the updates to download and install.
5. Restart Outlook and test.

For reference: Open Office apps in safe mode on a Windows PC - Microsoft Support

If none of the above solutions work, let me know for further investigation. Please note that our initial response does not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution.
Kind regards,

Kai-L - MSFT | Microsoft Community Support Specialist