`system-name' instead of both function and variable.
(defcustom gnus-local-domain nil
"Local domain name without a host name.
The DOMAINNAME environment variable is used instead if it is defined.
-If the `system-name' function returns the full Internet name, there is
+If the function `system-name' returns the full Internet name, there is
no need to set this variable."
:group 'gnus-message
:type '(choice (const :tag "default" nil)