Charles Lindsey <chl(_at_)clerew(_dot_)man(_dot_)ac(_dot_)uk> writes:
Since then, it has actually been implemented in some email systems
(notably those written by Dan Bernstein).
Also mutt and Gnus.
--
Russ Allbery (rra(_at_)stanford(_dot_)edu)
<http://www.eyrie.org/~eagle/>