Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann) writes:
> 
> I was hoping that it is possible to play tricks with
> adaptive-fill-regexp and adaptive-fill-first-line-regexp but couldn't
> find out how to do that quickly.

Below is something I came up with for a message-fill-paragraph.  It
seems to do mostly the right thing, someone smart can pick it up and
run with it, or kick it into touch.  To try it, start editing a
message and do

        (load "mfill.el")

Filling a long References: or Subject: is nice, but is it right to
fill mail addresses on space boundaries?  If not then the easy way of
just letting some variables might be doomed.

Kai, your new auto-fill-inhibit-regexp I guess won't inhibit on a
filled line in the headers, which is either good or bad depending on
your viewpoint.  If there's already some filling perhaps it's right to
do more.