Starting Outlook in safe mode is a useful diagnostic tool that can help you troubleshoot issues with the program. When you start Outlook in safe mode, it loads only basic drivers and services, which can help isolate the cause of any problems you may be experiencing. 

1. Close Outlook if it is currently open.
2. Hold down the CTRL key on your keyboard and double-click the Outlook icon.
3. When prompted, click Yes to start Outlook in safe mode.

That's it! Outlook will now start in safe mode, and you can begin diagnosing any issues you may be experiencing. Remember to restart Outlook normally once you have finished troubleshooting in safe mode.