A lot of the
largest ISPs have an <abuse> mailbox, which even generates pleasant-
sounding autoreplies, but there's considerable controversy whether
abuse complaints are acted upon...
It is pretty easy to provide empirical measures. Number of mails sent
to spampots for example.
We have to think in terms of a phased approach. There are multiple
spam problems. At the moment the criminal-spam problem swamps all
the rest.
I believe that the criminal spammers will fall at the first hurdle where
they are asked to provide an address where legal process can be served.
Then we can return to the problem of how to hold non-criminals
accountable for the email they send. That is where the performance and
consequences criteria are critical.
Phill