Re: draft-duan-smtp-receiver-driven-00.txt

On Wed, 11 May 2005 10:15:43 EDT, Hector Santos said:

> Call Back Verifiers (CBV) are also in place which is essentially a
> "SMTP-based challenge" to validate the reverse path, dynamically and only
> the spot, based on the theory that a Bounce Address must be correct as soon
> as it is provided.   This helps eliminates NXDOMAIN and bad email domains
> transactions.  Rejection are 45x based so a good system that is
> "temporarily" down will try again.  Bad Systems do not.
And how, exactly, does *my* system distinguish between "This is Hector's
stuff doing a call-back" and "This is a spammer doing listwashing"?
(Remember that at many sites, you will be connecting to an inbound MX which
can't correlate your callback to an outbound connection from the outbound
gateway).  Alternately phrased, what call-back scheme are you using that
I'm not likely to refuse because it looks like a data trawl of some sort?

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