RE: The Reg does 240/4

["Brotman, Alex via NANOG" <nanog () nanog org>]

We (comcast.net) have been sending/receiving via IPv6 since 2012 or so.  We do have PTR records for our outbound IPv6 
addresses, and expect them for inbound IPv6 as well.    Keeping in mind that a huge portion of inbound mail is 
bulk/commercial and they have thus far largely avoided IPv6, Inbound IPv6 is about 5% of traffic.  Outbound IPv6 is 
about 40% of traffic.  I’m not sharing mail submissions from users as many (nearly all?) of our users have IPv6 and 
that would skew the numbers, and may not be relevant to this discussion.

--
Alex Brotman
Sr. Engineer, Anti-Abuse & Messaging Policy
Comcast

From: NANOG <nanog-bounces+alex_brotman=comcast.com () nanog org> On Behalf Of Mike Hammett
Sent: Friday, February 16, 2024 10:20 AM
To: list () satchell net
Cc: nanog () nanog org
Subject: Re: The Reg does 240/4

"Does any IPv6 enabled ISP provide PTR records for mail servers?"

I think people will conflate doing so at ISP-scale and doing so at residential hobbiyst scale (and everything in 
between). One would expect differences in outcomes of attempting PTR records in DIA vs. broadband.

"How does Google handle mail from an IPv6 server?"

A few people have posted that it works for them, but unless it has changed recently, per conversations on the mailop 
mailing list, Google does not treat IPv6 and IPv4 mail the same and that causes non-null issues.



-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com<https://urldefense.com/v3/__http:/www.ics-il.com__;!!CQl3mcHX2A!Adj7UyXOfg2bkj9fl_CbY2Z7kBhqQzqvduQFbfMITlcG2Om1zcWSj6zljATvnM2kFdxDQer3FJBfv7AFbA$>

Midwest-IX
http://www.midwest-ix.com<https://urldefense.com/v3/__http:/www.midwest-ix.com__;!!CQl3mcHX2A!Adj7UyXOfg2bkj9fl_CbY2Z7kBhqQzqvduQFbfMITlcG2Om1zcWSj6zljATvnM2kFdxDQer3FJCDd4cxfw$>

________________________________
From: "Stephen Satchell" <list () satchell net<mailto:list () satchell net>>
To: nanog () nanog org<mailto:nanog () nanog org>
Sent: Wednesday, February 14, 2024 8:25:03 PM
Subject: Re: The Reg does 240/4

On 2/14/24 4:23 PM, Tom Samplonius wrote:
> The best option is what is happening right now:  you can’t get new IPv4
> addresses, so you have to either buy them, or use IPv6.  The free market
>   is solving the problem right now.  Another solution isn’t needed.

Really?  How many mail servers are up on IPv6?  How many legacy mail
clients can handle IPv6?  How many MTA software packages can handle IPv6
today "right out of the box" without specific configuration?

Does any IPv6 enabled ISP provide PTR records for mail servers?

How does Google handle mail from an IPv6 server?

The Internet is not just the Web.