How about doing the reverse --- requiring that all mail generated by
vacation-type programs be identified as such in the header (e.g. 'Content-type:
Vacation notice' or 'Precedence: total junk' or some such. Then LISTSERV (and
non-CMS mailing list bouncers) would simply look for this line, and list owners
/ postmasters would be fully justified in flaming folks/sites that run
non-complying vacation programs. One could start by making appropriate
modifications to the widely used 'vacation' program.
 
(Likewise, an RFC could *require* that bounced mail be identified as such in
standard manner in the header, and refuse to talk to sites that send out bounce
mail that can't be detected by LISTSERV (e.g., IBM.COM). But I guess this would
be too good...)
 
Dimitri Vulis