Lazy network operators

As far as your own incoming mail is concerned,
you get the same results by either requiring almost every ISP in the world
to block outgoing SMTP from almost all of their users,
or by using a blocking list that blocks the same users.
The blocking list approach preserves the end-to-end behavior of the Internet,
and lets the end users decide whose opinions to follow about
which Internet users are first-class citizens vs. second-class citizens.

  Of course, I was planning to write that comparison before
  the recent complaints about how bad a job SORBS is doing
  on deciding who to block. :slight_smile: But it's still equivalent.

If an ISP wants to be "responsible" about preventing untrustworthy users
from sending SMTP that bothers people, they can contribute to blocking lists
rather than dropping the users' packets, and the blocking lists can provide
some convenient mechanism for the ISPs to update them.

Where the two approaches diverge is that the recipient-based approaches
can also support whitelists, either individually run or
shared exception systems such as Habeas or bonded sender things,
while the ISP-blocking approach isn't something you can easily override,
except by doing tunneling or other protocol-heavy workarounds.

         Bill Stewart,

Unless you're using an AT&T nameserver it seems...