I've just submitted a new proposal as an Internet-Draft. It is
related to DRIP but uses an SRV record, rather than a new DNS record.
Until it appears, you can find a copy at:
<http://brandenburg.com/specifications/draft-crocker-marid-smtp-validate-00.txt>
Client SMTP Validation
draft-crocker-marid-smtp-validate-00.txt
SUMMARY
Internet mail suffers from the operation of hosts that
operate as mail transfer agents (MTA) without any
accountability. This makes it impossible to vet MTAs
or find recourse when their operation causes problems.
The current specification defines a modest mechanism
that permits session-time, domain-based validation of
peer, client MTAs without prior arrangement between the
MTAs. It provides a small, simple and useful
improvement to Internet mail service accountability.
It is based on well-understood mechanisms and is easily
deployed and used. Note that validation does not imply
that the MTA is well behaved, merely that it is
accountable to the cited domain administrator.
d/
--
Dave Crocker <mailto:dcrocker(_at_)brandenburg(_dot_)com>
Brandenburg InternetWorking <http://www.brandenburg.com>
Sunnyvale, CA USA <tel:+1.408.246.8253>, <fax:+1.866.358.5301>