Variable: message-required-mail-headers

message-required-mail-headers is a customizable variable defined in message.el.gz.

Value

(From Subject Date
      (optional . In-Reply-To)
      Message-ID
      (optional . User-Agent))

Documentation

Headers to be generated or prompted for when mailing a message.

It is recommended that From, Date, To, Subject and Message-ID be included. Organization and User-Agent are optional.

Source Code

;; Defined in /usr/src/emacs/lisp/gnus/message.el.gz
(defcustom message-required-mail-headers
  '(From Subject Date (optional . In-Reply-To) Message-ID
	 (optional . User-Agent))
  "Headers to be generated or prompted for when mailing a message.
It is recommended that From, Date, To, Subject and Message-ID be
included.  Organization and User-Agent are optional."
  :group 'message-mail
  :group 'message-headers
  :link '(custom-manual "(message)Message Headers")
  :type '(repeat sexp))