(defvar my-mh-keywords
   '(("^From: \\(.*\\)" 1 'bold t)
     ("^Subject: \\(.*\\)" 1 'highlight t))
  "mh-e additions for font-lock-keywords.")

(defun my-mh-show-mode-hook ()
  "Hook to turn on and customize fonts."
  (require 'font-lock)				; for font-lock-keywords below
  (make-local-variable 'font-lock-mode-hook)	; don't affect other buffers
  (add-hook 'font-lock-mode-hook	; set a hook with inline function
            (function			; modifies font-lock-keywords when
             (lambda ()			;   font-lock-mode run
               (setq font-lock-keywords 
                     (append my-mh-keywords font-lock-keywords)))))
  (font-lock-mode 1))			; change the typefaces

(if window-system			; can't do this on ASCII terminal
    (add-hook 'mh-show-mode-hook 'my-mh-show-mode-hook))