In trying to find a way to set mutt to have vim use 72 character line widths I found this page of MUTT and VIM - Tips and Tricks. Shows how to set up your .muttrc to execute vim with the right command line args for this, or set up an autocommand to match on /tmp/mutt* files, which is what mutt will use.
There are some other good ones in there. Pardon the page link, the original is this page but for some reason no browsers want to display it. Thanks for "view as html" google!
Here is another, page with some more mutt configuration hints. Heck, just head over to this page of configuration files for everything from vim to X. Probably out of date a bit, but hey, it's got pretty colors!