message-forward command pops up a message buffer to forward
the message in the current buffer. If given a prefix, forward using
nil, all headers that match this regexp will be deleted when forwarding a message.
nil, only headers that match this regexp will be kept when forwarding a message.
The provided functions are:
t, the subjects of forwarded messages have the evidence of previous forwards (such as ‘Fwd:’, ‘Re:’, ‘(fwd)’) removed before the new subject is constructed. The default value is
t(the default), forwarded messages are included as inline MIME RFC822 parts. If it's
nil, forwarded messages will just be copied inline to the new message, like previous, non MIME-savvy versions of Gnus would do.
nil, put forwarded message before signature, else after.