(defun spook-make-boundary nil
  (save-excursion
    (set-buffer (generate-new-buffer " *spook tmp*"))
    (setq buffer-disable-undo t)
    (spook)
    (subst-char-in-region (point-min) (point-max) ?\n ?= t)
    (subst-char-in-region (point-min) (point-max) ?   ?- t)
    (prog1 
	(buffer-substring (point-min) (min 70 (point-max)))
      (kill-buffer (current-buffer)))))

(require 'mml)
(defun mml-make-boundary nil (spook-make-boundary))