message-forward-included-headers

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

nil

Documentation:
If non-nil, delete non-matching headers when forwarding a message.
Only headers that match this regexp will be included. This
variable should be a regexp or a list of regexps.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 25.1 of Emacs.