Mail will wrap at the limit of the window.
Of course, you can always hard break or you can set the window to be the width you want it to be.
Just out of mere curiosity, how do you ensure that the person reading your email has their mail window, or reading pane, set to the same size as you.
Outlook, that well known Windows email program, does the same. Big window, long lines, small window, short lines
I have another question. Either my google-fu sucks, or there really isn't a way to make Mail in Mac OS X 10.6 break lines at a character length of my choice (like after 80 or so chars). My Mail doesn't break lines at all when I write an e-mail -- it just wraps them at the window border.
Please tell me I'm just missing some configuration option!