For BATV to be useful, a domain would have to be able to say that all
messages from that domain must have BATV tags. I can't see anything in the
spec to cover that requirement. Otherwise a spammer will just send messages
without BATV tags, and BATV will achieve nothing other than upsetting some
legitimate mailing lists...
The main goal of BATV is to deal with bounce blowback, that is, DSNs due
to spam sent with forged return addresses. If your domain is popular
among spammers, blowback can be a serious issue. On a bad day, my
abuse.net domain gets 400,000 bounces for mail it didn't send.
The only thing prvs accomplishes is to let you tell whether an incoming
bounce was sent in response to a message you actually sent. If you
know that you sign all your own mail, you can be reasonably sure that
bounces to signed addresses are real, and bounces to unsigned addresses
are fake, give or take the edge cases we've been discussing.
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
"I dropped the toothpaste", said Tom, crestfallenly.