Hi Gordon,
In your Preferences folder of the Library folder of your Home
directory there should be a plist document called
com.apple.mail.plist or something close to that. You can delete
this plist file and you'll at least get rid of some preferences. It
will rebuild the plist file upon restarting Mail. There are some
other items relating to Mail in the Library file where it keeps your
messages files for each account but I'm not totally sure as to it's
exact location.
Later...
Tim Kilburn
& Carter the Canine
Fort McMurray, AB Canada