The problem is that nothing works in all cases. If not sending inappropriate
vacation notices is a top priority (and I think it should be), then a
combination of techniques is needed. And this is exactly what the
sieve vacation notice draft (draft-showalter-sieve-vacation-04.txt) does.
(It also requires that such notices be sent to the envelope from.)
The above I-D has expired, although I could find copies of it.
Tim, what is the status of draft-showalter-sieve-vacation?
<http://debian.ens-cachan.fr/ftp/mirror/RFC/internet-drafts/draft-showalter-si
eve-vacation-04.txt.gz>
-d