why IPv6 isn't ready for prime time, SMTP edition

Laszlo Hanyecz laszlo at heliacal.net
Tue Mar 25 21:33:41 UTC 2014

The usefulness of reverse DNS in IPv6 is dubious.  Maybe the idea is to cause enough pain that eventually you fold and get them to host your email too.


On Mar 25, 2014, at 8:57 PM, Brielle Bruns <bruns at 2mbit.com> wrote:

> On 3/25/14, 11:56 AM, John Levine wrote:
>> I think this would be a good time to fix your mail server setup.
>> You're never going to get much v6 mail delivered without rDNS, because
>> receivers won't even look at your mail to see if it's authenticated.
>> CenturyLink is reasonably technically clued so it shouldn't be
>> impossible to get them to fix it.
> Nothing wrong with my mail server setup, except the lack of RDNS. Lacking reverse should be one of many things to consider with rejecting e-mails, but should not be the only condition.
> That would be like outright refusing mail unless it had both SPF and DKIM on every single message.
> Sure, great in theory, does not work in reality and will result in lost mail from legit sources.
> Already spoken to CenturyLink about RDNS for ipv6 - won't have rdns until native IPv6.  Currently, IPv6 seems to be delivered for those who want it, via 6rd.
> And, frankly, I'm not going to get in a fight with CenturyLink over IPv6 RDNS, considering that I am thankful that they are even offering IPv6 when other large providers aren't even trying to do so to their residential and small business customers.
> It is very easy for some to forget that not everyone has a gigabit fiber connection to their homes with ARIN assigned IPv4/IPv6 blocks announced over BGP.  Some of us actually have to make do with (sometimes very) limited budgets and what the market is offering us and has made available.
> -- 
> Brielle Bruns
> The Summit Open Source Development Group
> http://www.sosdg.org    /     http://www.ahbl.org

More information about the NANOG mailing list