For all my supposed geekiness, I haven’t been able to send mail from Thunderbird since I upgraded my operating system several months ago (and did a brand new install of Thunderbird, etc, etc). I attribute this to:
a) Bill Gates
b) My outgoing mail server
c) Stealthy unseen forces and gremlins
d) General laziness
Basically, don’t send stuff for which you want a reply to my NicoleSwan.com email address. If it’s read-only, go ahead and send it.