Variable: rfc2047-header-encoding-alist

rfc2047-header-encoding-alist is a customizable variable defined in rfc2047.el.gz.

Value

(("Newsgroups")
 ("Followup-To")
 ("Message-ID")
 ("Content-Disposition" . default)
 ("\\(Resent-\\)?\\(From\\|Cc\\|To\\|Bcc\\|\\(In-\\)?Reply-To\\|Sender\\|Mail-Followup-To\\|Mail-Copies-To\\|Approved\\|Disposition-Notification-To\\)" . address-mime)
 (t . mime))

Documentation

Header/encoding method alist.

The list is traversed sequentially. The keys can either be header regexps or t.

The values can be:

1) nil, in which case no encoding is done;
2) mime, in which case the header will be encoded according to RFC2047;
3) address-mime, like mime, but takes account of the rules for address
   fields (where quoted strings and comments must be treated separately);
4) a charset, in which case it will be encoded as that charset;
5) default, in which case the field will be encoded as the rest
   of the article.

Source Code

;; Defined in /usr/src/emacs/lisp/mail/rfc2047.el.gz
(defcustom rfc2047-header-encoding-alist
  '(("Newsgroups" . nil)
    ("Followup-To" . nil)
    ("Message-ID" . nil)
    ;; This header must be pre-encoded by the MTA, so avoid
    ;; double-encoding it.
    ("Content-Disposition" . default)
    ("\\(Resent-\\)?\\(From\\|Cc\\|To\\|Bcc\\|\\(In-\\)?Reply-To\\|Sender\
\\|Mail-Followup-To\\|Mail-Copies-To\\|Approved\\|Disposition-Notification-To\\)" . address-mime)
    (t . mime))
  "Header/encoding method alist.
The list is traversed sequentially.  The keys can either be
header regexps or t.

The values can be:

1) nil, in which case no encoding is done;
2) `mime', in which case the header will be encoded according to RFC2047;
3) `address-mime', like `mime', but takes account of the rules for address
   fields (where quoted strings and comments must be treated separately);
4) a charset, in which case it will be encoded as that charset;
5) `default', in which case the field will be encoded as the rest
   of the article."
  :type '(alist :key-type (choice regexp (const t))
                :value-type (choice (const nil) (const mime)
                                    (const address-mime)
                                    coding-system
                                    (const default))))