Variable: message-directory
message-directory is a customizable variable defined in message.el.gz.
Value
"~/Mail/"
Documentation
Directory from which all other mail file variables are derived.
Source Code
;; Defined in /usr/src/emacs/lisp/gnus/message.el.gz
(defcustom message-directory "~/Mail/"
"Directory from which all other mail file variables are derived."
:group 'message-various
:type 'directory)