how do i reset my mail app to factory settings

Go to Library and rename Mail as Mail-old

Setup a new user account. Copy the Mail folder from there to your account.

Why can't you just simply go to Mail preferences, and then click on accounts tab, and hit the - button to delete any accounts you have set up.

Hackinosh, that solution doesn't always work.

The problem I am having is that I can't delete an account that keeps crashing Mail. It is an iCloud account and if I take it offline Mail will work again, but if I go to preferences to delete that account, it crashes again just by my clicking on that account in Preferences, even though it is still offline. I have sent Apple a ballizillion crash reports by now.

I think I will back up the working accounts and try renaming the Mail folder so I can start over. Will report back if successful.