Cannot renew configuration of mail account

When I delete one of my mail account, and then try to add it again - it add it again with the same corrupted settings, and I can't connect to my mail server (with proper login and password - I think some settings inside my Mail are corrupted somehow).

I need to delete configuration files, not through "add/remove" system settings. Where are the stored on my mac?

And I mean config files, not ~/Library/Mail files.

can you tell me the path to them?