Emacs w32 as external editor in Thunderbird

["B. T. Raven" <nihil@nihilo.net>]

I have (server-start) in my .emacs and this allows me to click on files
in Windows Explorer with associated extensions and have them all open in
a unique instance of Emacs. When I click on Emacs icon or do Ctl-E in
Tbird, not only is a new instance of Emacs opened, but somehow an
implicit (server-mode -1) seems to be called, or something that requires
me to issue M-x server-start from within the original session in order
to have clicked on files open in that original emacs instance.
Can any of you tell me what is going on? I have ALTERNATE_EDITOR
environment variable set to C:\emacs\bin\runemacs.exe and
emacsclientw.exe somewhere appropriate in the registry (win2000); at
least server functionality works if I don't try to call it through
Thunderbird.

Thanks,

Ed