On Tue, 2004-07-20 at 18:49, Nico Kadel-Garcia wrote:
All well and good, and it does precisely what you described. It's an SPF
specific usage: it's not a general requirement of DNS, and I really consider
it important that people be clear on that.
Another way of looking at it is that the DNS-based mechanisms used in
SPF (a & mx) are based on the DNS records of the domain owner for the
domain concerned. However, PTR records are potentially controlled by
unknown parties, so the confirmation check of doing the forward lookup
on the returned PTR record is needed to bring control back into the
hands of the original domain owner.
Paul.
--
Paul Howarth <paul(_at_)city-fan(_dot_)org>