Let's get this clear - you said "Firefox". I take it you meant Thunderbird?

I stand corrected. Thunderbird is trying to connect to a deleted account and I have completely deleted and reloaded Thunderbird with no gain. The problem account does not exist in Tools/account settings.

Something has gone rather horribly wrong. The settings that Thunderbird is using can only come from its profile, but if the account has gone from the settings and yet the account is still being accessed, then the settings page has become out of step with the true state of the profile. Note that uninstalling and reinstalling the Thunderbird program is generally ineffective as the settings are held separately in its profile folder.

I'd go to Tools|Options|Advanced>Configuration Editor and look there for references to the unwanted account and see if they can be deleted there. If that fails, I'd close Thunderbird and look through the js files in a text editor. If you do this, be sure to make backups, because if the preference files are improperly formatted, Thunderbird may fail to start.

Thank you!!!! That was it. There was a search string pointing to the deleted account and after resetting it, problem solved.

Thanks again, you're awesome!