Variable: message-newgroups-header-regexp
message-newgroups-header-regexp is a customizable variable defined in
message.el.gz.
Value
"^\\(Newsgroups\\|Followup-To\\|Posted-To\\|Gcc\\):"
Documentation
Regexp matching headers that list groups.
Source Code
;; Defined in /usr/src/emacs/lisp/gnus/message.el.gz
;;; Group name and email address completion.
(defcustom message-newgroups-header-regexp
"^\\(Newsgroups\\|Followup-To\\|Posted-To\\|Gcc\\):"
"Regexp matching headers that list groups."
:group 'message
:type 'regexp)