HTML or Plain in T-Bird; That is the Question....

[Joseph]

I know I've been stirring things up here since I got Ubuntu.  However, 
I'll ask anyway.

I'm using T-Bird for my mail.  There's one thing that I want to alter;  
that's the question I get when I send an eMail.  It asks if I want to 
mail it in HTML, plain, or both.  How can I shut that off?

Joseph