On 9/27/20 11:40 AM, John R Levine wrote:
I would say instead that because some subset of inbound MTAs do EHLO
verification, "real mail servers" (i.e. those which manage to
continue to deliver mail with some reliability) are forced to have
static IPv4 source addresses for which PTR lookup results match EHLO
arguments.
No, we've observed in practice that hosts that don't have matching
PTRs are spambots.
I don't believe that anyone takes enough time to look at a sufficient
volume of email, often enough, to be sure of that. And again, it's a
self-fulfilling belief.
Anything that comes from a dynamic or NAT pool is invariably spam
from a botnet.
No, because nobody is looking that closely.
Sorry, but you're just wrong. We absolutely look that closely. I
know people who maintain pools of patterns to recognize dynamic pool
rDNS which lots of people use in their spam scoring.
I didn't say it wasn't used, I said it wasn't reliably measured.
It would be nice if mail still worked the way it did 30 years ago, but
that was most definitely then, and this is now.
And poorly chosen spam filters are a big reason for the degradation of
email reliability during that time.
Keith
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