Daniel Taylor wrote:
Stuart D. Gathman wrote:
I get the picture. So IPv4 is officially unusable for us poor folk.
I guess I need to start figuring out how to set up IPv6 email, where
I can set my own rDNS.
How do I send from an IPv6 address if the MX records for the
destination domain list only IPv4 hosts? Use a relay with SMTP AUTH?
Who offers such a service? All IPv4 SMTP relays I've seen don't
prevent cross-customer forgery (except maybe Kitterman's), so you are
actually *more* likely to get forged mail if you force me to go that
route. Seems counter productive.
Delegating PTR for anything less than a full /24 network block does
not appear to be practical, if it is even possible.
RFC 2317. In short, you use CNAMEs in the x.x.x.in-addr.arpa zone. You can
delegate IP subnets of a /25 or smaller size this way, or directly map a
handful of IP addresses to an arbitrary domain under the customer's control.
Our ISP has done exactly this; they map our reverse IP addresses using CNAMEs
to addresses in the rev.3sharp.com domain.
In the past eight years, I've had no problems getting any of my ISPs to do
this. To forestall the inevitable arguments, I am aware that living in the
Seattle area blesses me with a plethora of cluefull IPS admins who cater to the
geek crowd. However, I know many people around the world who have gotten their
ISPs to implement some sort of forwarding. Having an RFC to wave at them helps
a lot; it assures them this is a standard practice, not some weird one-off.
--
Devin L. Ganger, Exchange MVP Email: deving(_at_)3sharp(_dot_)com
3Sharp LLC Phone: 425.882.1032 x1011
14700 NE 95th Suite 210 Cell: 425.239.2575
Redmond, WA 98052 Fax: 425.702.8455
(e)Mail Insecurity: http://blogs.3sharp.com/blog/deving/
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