Force Mail to Display All Messages as Plain Text

From Ben's Writing

For one reason or another, I've grown used to viewing my email in plain text, and having to continually subject myself to other people's idea of a good font is irksome, to say the least. I've had my system configured to hide all the jazz from me for sometime, but I have no refenrece for how I did it originally. It seems the simplest method to put this in effect is:

$ defaults write com.apple.mail PreferPlainText -bool TRUE