Managing personal Outlook.com account settings, security, and privacy
Hi Wilhelm,
Thank you for posting your problem, I am here to help you today. Possible reason you are getting this problem is because of a corrupted profile, a problematic add-in, or a corrupt Outlook data file.
To fix this problem try this method: Check for Running Processes. Press Ctrl + Alt + Delete to open the Task Manager and look for any instances of Outlook. Click / highlight Outlook then End these processes and try opening Outlook Classic again.
Let me know how this goes. Looking forward to helping you out. If you need more help please feel free to let me know.
Best regards,
Jansher