Variable: message-replacement-char
message-replacement-char is a customizable variable defined in
message.el.gz.
Value
"."
Documentation
Replacement character used instead of unprintable or not decodable chars.
This variable was added, or its default value changed, in Emacs 22.1.
Source Code
;; Defined in /usr/src/emacs/lisp/gnus/message.el.gz
(defcustom message-replacement-char "."
"Replacement character used instead of unprintable or not decodable chars."
:group 'message-various
:version "22.1" ;; Gnus 5.10.9
:type '(choice string
(const ".")
(const "?")))