----- Original Message -----
From: "Paul Howarth" <paul(_at_)city-fan(_dot_)org>
What he means is that the reverse DNS lookup of 207.34.104.6 having a
PTR record pointing to 207-34-104-6.ip.cal.radiant.net is not trusted to
be reliable unless a forward lookup of the name
207-34-104-6.ip.cal.radiant.net yields an A record of value 207.34.104.6
(which it does).
This would have no effect whatsoever on anyone's SPF setup unless they
specified a PTR mechanism for the domain radiant.net, cal.radiant.net
etc. as indicating valid senders for their domain.
Paul.
Well said. Despite my carping, it's actually *possible* to make these things
definitive for a domain, but it requires the use of matching *singular* PTR
and A records for the hostnames. This is possible for domains that have
excellent control of their DNS, but not for a large percentage of domains.
In particular, it breaks down badly for SMTP servers that host multiple
domains, such as many of the ones that folks on this list administrate.