On Thu, 17 Jan 2008 14:46:50 -0500, Joe wrote:

Now if I can just figure out how to get the message body to open in a
new window (as a default), without having to do any extra clicking on
window icons. Thunderbird defaults to the 3 pane display, but if I
drag the middle border down (which closes off the message body), it
defaults to opening the message in a new window. That way, I get to
see more of the thread view, which helps me to decide how I want to
proceed.

Not exactly what your looking for, but single pane display is close and
what I use 99% of the time.

On the right hand edge, slightly below the close "X" is a square. Click
it with the mouse and your in single pane. (It is a toggle so a second
click will go back to 3 pane.) While in single pane you can use the "n"
key to go to the next unread message, or the tabs to go to the other two
panes.
--
William