I have a number of email personalities and they were all configurable
under the menu Tools/Account settings.

Recently, one of them, (this one) has disappeared from the list in the
menu, but is still available in the compose window "From" drop down box.
I just can't change anything in it. I tried creating another, but
then I got two in the compose drop down. Not what I wanted.

Any ideas, or if not, where can I find the config file (if it's an
editable text file)?