Variable: rmail-displayed-headers
rmail-displayed-headers is a customizable variable defined in
rmail.el.gz.
Value
nil
Documentation
Regexp to match Header fields that Rmail should display.
If nil, display all header fields except those matched by
rmail-ignored-headers.
Source Code
;; Defined in /usr/src/emacs/lisp/mail/rmail.el.gz
;;;###autoload
(defcustom rmail-displayed-headers nil
"Regexp to match Header fields that Rmail should display.
If nil, display all header fields except those matched by
`rmail-ignored-headers'."
:type '(choice regexp (const :tag "All" nil))
:group 'rmail-headers)