gnus-header-button-alist

gnus-header-button-alist is a variable defined in `gnus-art.el'.
Its value is shown below.

• This variable may be risky if used as a file-local variable.

Documentation:
*Alist of headers and regexps to match buttons in article heads.

This alist is very similar to `gnus-button-alist', except that each
alist has an additional HEADER element first in each entry:

(HEADER REGEXP BUTTON FORM CALLBACK PAR)

HEADER is a regexp to match a header. For a fuller explanation, see
`gnus-button-alist'.

You can customize this variable.

Value:

(("^\\(References\\|Message-I[Dd]\\|^In-Reply-To\\):" "<[^<>]+>" 0
  (>= gnus-button-message-level 0)
  gnus-button-message-id 0)
 ("^\\(From\\|Reply-To\\):" ": *\\(.+\\)$" 1
  (>= gnus-button-message-level 0)
  gnus-button-reply 1)
 ("^\\(Cc\\|To\\):" "[^ 	\n<>,()\"]+@[^ 	\n<>,()\"]+" 0
  (>= gnus-button-message-level 0)
  gnus-msg-mail 0)
 ("^X-[Uu][Rr][Ll]:" gnus-button-url-regexp 0
  (>= gnus-button-browse-level 0)
  browse-url 0)
 ("^Subject:" gnus-button-url-regexp 0
  (>= gnus-button-browse-level 0)
  browse-url 0)
 ("^[^:]+:" gnus-button-url-regexp 0
  (>= gnus-button-browse-level 0)
  browse-url 0)
 ("^OpenPGP:.*url=" gnus-button-url-regexp 0
  (>= gnus-button-browse-level 0)
  gnus-button-openpgp 0)
 ("^[^:]+:" "\\bmailto:\\([-a-z.@_+0-9%=?&/]+\\)" 0
  (>= gnus-button-message-level 0)
  gnus-url-mailto 1)
 ("^[^:]+:" "\\(<\\(url: \\)?\\(nntp\\|news\\):\\([^>\n ]*\\)>\\)" 1
  (>= gnus-button-message-level 0)
  gnus-button-message-id 4))