(add-to-list 'auto-mode-alist
             '("\\`/tmp/mutt-[^/]+\\'" . mail-mode)) 

(add-hook 'mail-mode-hook
          '(lambda ()
             (auto-fill-mode 1)
             (set (make-local-variable 'tab-stop-list)
                  (number-sequence 4 100 4))
             (setq indent-tabs-mode nil
                   fill-column 72)
             (when (>= emacs-major-version 23)
               (visual-line-mode 1)))) 

(autoload 'longlines-mode "longlines.el" "Minor mode for editing long lines." t)
(add-hook 'text-mode-hook 'longlines-mode)