Variable: rmail-highlighted-headers
rmail-highlighted-headers is a customizable variable defined in
rmail.el.gz.
Value
"^From:\\|^Subject:"
Documentation
Regexp to match Header fields that Rmail should normally highlight.
A value of nil means don't highlight. Uses the face rmail-highlight.
Probably introduced at or before Emacs version 19.23.
Source Code
;; Defined in /usr/src/emacs/lisp/mail/rmail.el.gz
;;;###autoload
(defcustom rmail-highlighted-headers "^From:\\|^Subject:"
"Regexp to match Header fields that Rmail should normally highlight.
A value of nil means don't highlight. Uses the face `rmail-highlight'."
:type '(choice regexp (const :tag "None" nil))
:group 'rmail-headers)