Variable: message-header-use-obsolete-in-reply-to
message-header-use-obsolete-in-reply-to is a customizable variable
defined in message.el.gz.
Value
nil
Documentation
Include extra information in the In-Reply-To header.
This form has been obsolete since RFC 2822.
This variable was added, or its default value changed, in Emacs 31.1.
Probably introduced at or before Emacs version 31.1.
Source Code
;; Defined in /usr/src/emacs/lisp/gnus/message.el.gz
(defcustom message-header-use-obsolete-in-reply-to nil
"Include extra information in the In-Reply-To header.
This form has been obsolete since RFC 2822."
:group 'message-headers
:version "31.1"
:type 'boolean)