ms office – Outlook for Mac 2011: how to delete e-mail with errors in the outbox that blocks Outlook

I have an email in my Outbox that continuously blocks Outlook for Mac 2011 with an error message "rebuild the database". The reconstruction of the database took days and was never completed. If I start Outlook in safe mode (holding down the Shift key when loading), I can access Outlook, but at the moment I press Send / Receive or switch to the Outbox folder (where the guilty email is located) , I immediately receive the "reconstruction" error message "database" and can Rebuild or Cancel, the latter leaves Outlook.

Is there any way to empty the Outbox folder through the file system without clicking on the folder in Outlook? Any other solution?

Thank you.