nanog mailing list archives
Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption")
From: "John Levine" <johnl () iecc com>
Date: 3 Oct 2015 19:07:36 -0000
One thing that I thought was going to be a huge help with sending-IP blacklists in the IPv6 world... was perhaps shifting to tighter standards and greater reliance for Forward Confirmed rDNS (FCrDNS).
A lot of IPv6 mail systems want you to use SPF and DKIM signatures on IPv6 mail, or they won't accept it. This is a frequent topic at MAAWG meetings. IPv6 rDNS is a can of worms. You can't do generic rDNS other than with a stunt server that generates results on the fly. The general agreement seems to be that servers (which include mail clients) should have static IPs and valid rDNS, but the pain of doing rDNS at all has made the rDNS flaky. And anyway, a DKIM signature or even an SPF record is a lot more informative than a PTR record.
For example, if a spammer who has acquired a /48 is sending from literally millions, perhaps billions, of DIFFERENT IPs on that /48, ...
Even with a /64 a spammer could easily use a different IP for every message he ever sent, which as you note would make both legitimate bounce handling and spammer list washing easier. That's why no DNSBL I know is interested in granularities less than /64. There are some hosting providers that due to poor choices made a few years back (and perhaps poorly designed equipment from vendors) have been giving customers each a /128 inside a shared /64, but the advice I've been seeing is that if you want your customers to be able to send mail, don't do that. R's, John
Current thread:
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption"), (continued)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Stephen Satchell (Oct 02)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Chris Adams (Oct 02)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Owen DeLong (Oct 03)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Justin M. Streiner (Oct 02)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Owen DeLong (Oct 03)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Owen DeLong (Oct 02)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Scott Morizot (Oct 03)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Randy Bush (Oct 03)
- RE: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Frank Bulk (Oct 03)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Rob McEwen (Oct 03)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") John Levine (Oct 03)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Barry Shein (Oct 04)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") William Herrin (Oct 03)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Owen DeLong (Oct 03)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Owen DeLong (Oct 02)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") cortana5 () gmail com (Oct 02)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Rob McEwen (Oct 01)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force Joe Greco (Oct 02)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Stephen Satchell (Oct 02)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") Måns Nilsson (Oct 06)
- Re: How to wish you hadn't forced ipv6 adoption (was "How to force rapid ipv6 adoption") George Michaelson (Oct 06)