Variable: mail-hist-header-regexp
mail-hist-header-regexp is a variable defined in mail-hist.el.gz.
Value
"^[^:]*:"
Documentation
Regular expression for matching headers in a mail message.
Source Code
;; Defined in /usr/src/emacs/lisp/mail/mail-hist.el.gz
;; (start . end) A pair indicating the buffer positions delimiting the
;; last inserted history, so it can be replaced by a new input if the
;; command is repeated.
(defvar mail-hist-header-regexp "^[^:]*:"
"Regular expression for matching headers in a mail message.")