>>>>> "David" == David Saez Padros <[EMAIL PROTECTED]> writes:

 >> But you're forcing me to devote _my_ resources to protecting
 >> _your_ network. How is this not abusive?

 David> First, i'm not only protecting my network, i'm also protecting
 David> your domain from people who try to send email on your's domain
 David> behalf to my users.

Did I ask you to do this?

 David> and you are missing one very important point, current smtp
 David> schema is by itself insecure, there is no widely spread way to
 David> check that the sender has relaly sent the message.

And callout does NOT HELP THIS AT ALL, since the spammers are quite
happy to use sender addresses that exist.

 David> This is a security problem that obviously when solved will
 David> imply that the receiver host will try to check the message
 David> auhtenticity by connecting to the sender's domain servers
 David> (SPF, DKIM, callout, whatever ...) Will you call this abuse ??

DNS has both positive and negative caching with TTLs specified by the
publisher; it is commonly cached in ways that allow sharing of caches
over many servers and users; it's a very lightweight protocol from the
point of view of an authoritative server; it is easily scaled up; the
relevent queries for SPF, DKIM, etc., are per-domain rather than
per-user, and it _exists for the purpose of publishing information
about domains_.  None of this is true for SMTP-based callouts.

-- 
Andrew, Supernews
http://www.supernews.com


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