message-forward-ignored-headers

message-forward-ignored-headers is a variable defined in `message.el'.
Its value is

"^Content-Transfer-Encoding:\\|^X-Gnus"

Documentation:
*All headers that match this regexp will be deleted when forwarding a message.
This may also be a list of regexps.

You can customize this variable.

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