I think that it is important to point out that you are not going to
get good results from naïve learning schemes and make sure that there
is sufficient coverage there to defend against the objection.
It seems to me the important point is that bad guys can and will
implement any technical spec that anyone can think up.
This means that it is foolish to assume that the mere presence of a
DKIM signature or any other technical detail means anything good about
a message. This is true whether it is people or software making the
NOTE WELL: This list operates according to