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

Brielle Bruns bruns at 2mbit.com
Wed Mar 26 02:31:15 UTC 2014

On 3/25/14, 8:03 PM, Robert L Mathews wrote:
> I don't quite see how this is anything to do with IPv6.

It does when you've got the job of trying to convince people who know 
nothing about how the internet works why they should invest time in 
something new.

Unless, I'm wrong in that we're trying to encourage people to go dual 
stacked and not be solely dependent on IPv4...

> If you set up an IPv4 mail server with no reverse DNS, your mail would
> be rejected by many servers, too. And there are certainly plenty of
> providers who won't let you configure the reverse DNS of an IPv4 address.

Yup, there are, and i've been on those providers in the past that did 
not consider IPv4 rdns important either.  Google does not outright 
reject mail from hosts with no IPv4 rdns, from what my quick test a 
moment ago showed.

> Your provider assigned you an IP address with no reverse DNS, and you
> set up a mail server on that IP address. Most people would say that was
> unreliable even before knowing you're talking about IPv6 instead of
> IPv4. <shrug>

Considering at the time of the deployment, I had no inclination that 
Google had enacted this policy, you can imagine my surprise, esp. after 
having said customer on an IPv4 addr previously that had no rdns either, 
and was sending mail to gmail fine.

Call it unreliable all you want, there's more then a few mail servers 
out there with no rdns on both IPv4 and IPv6.

Brielle Bruns
The Summit Open Source Development Group
http://www.sosdg.org    /     http://www.ahbl.org

More information about the NANOG mailing list