Hmm...I did everything in mdg's post with the exception of one thing if I have done it wrong. I got confused about this line in mdg's post:
3- Create a file called user.js in your ~/.thunderbird/default.xxx/ containing :
I have a ~./thunderbird/"defaults" directory with four sub directories inside it: "isp", "messenger", "pref", "profile". I'm assuming that the user.js file goes in the "pref" directory but I'm not sure. Actually I put it right into the "defaults" directory and not into a sub dir of "defaults". That maybe why it doesn't work.
Also, yes I am sure that I changed all of the paths in the two files to fit my system. I'm sure that would have been a question.
Lastly, thank you for moving the thread. I wasn't really sure where I should have put it.