message-forward-as-mime

message-forward-as-mime is a variable defined in `message.el'.
Its value is

t

Documentation:
*Non-nil means forward messages as an inline/rfc822 MIME section.
Otherwise, directly inline the old message in the forwarded message.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 21.1 of Emacs.