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

John Levine johnl at iecc.com
Tue Mar 25 17:56:03 UTC 2014

In article <5331C054.8040801 at 2mbit.com> you write:
>On 3/25/14, 11:23 AM, John Levine wrote:
>> Large mail providers all agree that v6 senders need to follow good
>> mail discipline, but are far from agreeing what that means.  It
>> certainly means proper rDNS, but does it mean SPF?  DKIM on all the
>> mail?  TLS on the connections?  At this point, I don't know and
>> neither does anyone else.  Fortunately we have at least another decade
>> of full IPv4 mail connectivity to figure it out.
>So, what's everyone's feelings about a rather large provider who blocks 
>IPv6 e-mail that has no RDNS, even though the sending domain has SPF 
>records allowing the block, and proper DKIM set up?
>*looks directly at Google*

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.


More information about the NANOG mailing list