Outlook may run slowly, freeze, or crash unexpectedly. This is often caused by a third-party add-in that is not working correctly. Add-ins are small programs that add features to Outlook. This article explains how to start Outlook in Safe Mode to disable all add-ins and then re-enable them one by one to find the problematic one.
Key Takeaways: Finding Problematic Outlook Add-Ins
- Outlook Safe Mode (/safe): Starts Outlook with all add-ins disabled to test if they are the cause of poor performance.
- File > Options > Add-ins > COM Add-ins > Go: Opens the dialog to manually disable or enable individual add-ins for testing.
- One-by-one enable method: The systematic process of re-enabling add-ins individually to isolate the one causing the slowdown.
Why Add-Ins Can Slow Down Outlook
Add-ins integrate with Outlook to provide extra functions like CRM tools, PDF creation, or meeting schedulers. They load every time you start the application. A poorly coded, outdated, or conflicting add-in can use excessive system resources. This leads to slow email sending, lag when switching folders, or Outlook becoming unresponsive. Performance issues often appear after installing new software or a Windows update that breaks add-in compatibility.
Safe Mode is a diagnostic state in Outlook. It prevents all add-ins, custom toolbars, and some settings from loading. If Outlook runs smoothly in Safe Mode, you can confirm an add-in is the root cause. The next step is to identify the specific add-in by enabling them individually and observing performance after each one.
Steps to Start Outlook in Safe Mode and Test Add-Ins
Follow these steps to diagnose which add-in is affecting Outlook’s performance.
- Close Outlook completely
Ensure Outlook is not running in the background. Right-click the Windows Start button, select Task Manager, and end any Outlook processes. - Open the Run dialog
Press the Windows key + R on your keyboard. This opens the Run command box. - Launch Outlook in Safe Mode
Typeoutlook.exe /safein the Run dialog and press Enter. A confirmation dialog may appear; click OK to proceed. - Test performance in Safe Mode
Use Outlook for a few minutes. Try opening emails, switching folders, and sending a test message. If the speed improves significantly, an add-in is likely the problem. - Access the Add-ins management window
With Outlook open normally, go to File > Options. Select the Add-ins category on the left. At the bottom, ensure COM Add-ins is selected in the Manage dropdown, then click the Go button. - Disable all add-ins
In the COM Add-Ins dialog, uncheck every box in the list to disable all items. Click OK and restart Outlook when prompted. - Re-enable add-ins one by one
Restart Outlook and note the performance. Go back to File > Options > Add-ins > Go. Enable the first add-in by checking its box. Click OK, restart Outlook, and test performance again. Repeat this process for each add-in. - Identify the problematic add-in
When you enable an add-in and Outlook becomes slow or crashes again, you have found the cause. Return to the COM Add-Ins dialog and permanently disable that specific add-in.
Alternative Method: Using the Windows Start Menu
- Hold the Ctrl key while starting Outlook
Click the Windows Start button, find the Outlook icon, but do not click it yet. Press and hold the Ctrl key on your keyboard, then click the Outlook icon. Keep holding Ctrl until a dialog appears. - Choose Safe Mode
A Microsoft Outlook dialog box will ask if you want to start in Safe Mode. Click Yes. This achieves the same result as using the Run command.
If the Problem Persists After Disabling Add-Ins
Outlook is Still Slow in Safe Mode
If performance issues continue even in Safe Mode, the problem is not related to add-ins. The cause could be a large mailbox, a corrupted Outlook data file, or system resource limitations. Proceed by repairing your Outlook data file via the Control Panel’s Mail setup or freeing up space in your mailbox.
An Add-In Re-enables Itself Automatically
Some add-ins are managed by other programs and may reactivate. If a disabled add-in reappears as enabled, you may need to uninstall the parent program. Use Windows Settings > Apps > Apps & features to find and uninstall the software associated with the add-in.
You Cannot Find the COM Add-ins Dialog
If the Go button is grayed out, you might be looking at a different add-in type. In the Manage dropdown at the bottom of the Add-ins window, select COM Add-ins. If it is not listed, your version of Outlook may use a different management interface, such as for web add-ins installed from the Office Store.
Outlook Startup Modes Comparison
| Item | Normal Mode | Safe Mode (/safe) |
|---|---|---|
| Add-ins Loaded | All enabled add-ins load | No add-ins load |
| Custom Toolbars | Fully available | Not available |
| Startup Speed | Can be slow if add-ins conflict | Typically faster |
| Primary Use | Daily work with all features | Diagnosing crashes and slowdowns |
| Extended Commands | Outlook.exe | Outlook.exe /safe, Outlook.exe /cleanviews |
You can now pinpoint which add-in is slowing down Outlook and disable it to restore performance. After identifying the faulty add-in, check the developer’s website for an updated version. For advanced management, use the Windows Registry Editor to permanently block an add-in from loading by navigating to HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\Addins.