-----Original Message-----
From: owner-ietf-smtp(_at_)mail(_dot_)imc(_dot_)org
[mailto:owner-ietf-smtp(_at_)mail(_dot_)imc(_dot_)org] On Behalf Of John C
Klensin
Sent: Wednesday, October 26, 2011 8:23 AM
To: Tim Kehres; Hector; ietf-smtp(_at_)imc(_dot_)org
Subject: Re: new draft: draft-santos-smtpgrey-01
While it might not help significantly, something more generic
would at least slightly and temporarily lower the odds of a
different problem. I really worry about saying to the spammer
"this site does greylisting" and, if that happens enough, having
the spammer respond (internally) "ah, it is greylisting and not
some random temporary server unavailability, we know what to do
about that".
[...]
Fully agree. I think the only possible mitigation would be a whitelist of
domains that are known to be legitimate and want this information, and then the
server returns these more informative replies since there's been some trust
established. In all other cases, a generic 4xy is returned when greylisting.
But that only adds further complexity.