I think checking the HELO *alone* is not an adequate solution to the
problem set. I don't think CSV alone is enough to be effective
against spam coming from big ISPs, where good and bad mail may flow
from the same MTA.
With any MTA of any size, you're going to get a mix of good and bad
mail.
A fairly fundamental question is whether we consider that to be a fact
of life that MTA operators can't control, or we consider MTA operators
to be responsible for the mail that they send, and evalute them in
view of their entire mail stream.
I realize that opinions differ, but I would like to see a scheme like
CSV that uses an IP address to identify an MTA, and handle individual
messages using something like Domain Keys that authenticates the
message itself rather than a probably shared message source.
Regards,
John Levine, johnl(_at_)iecc(_dot_)com, Primary Perpetrator of "The Internet
for Dummies",
Information Superhighwayman wanna-be, http://www.johnlevine.com, Mayor
"I shook hands with Senators Dole and Inouye," said Tom, disarmingly.