Gmail (thus Nanog) rejecting ipv6 email

Sat Apr 2 23:19:01 UTC 2022

On 4/2/22 3:56 PM, Jeroen Massar wrote:
>
>> On 3 Apr 2022, at 00:29, Michael Thomas <mike at mtcc.com> wrote:
>>
>>
>> On 4/2/22 3:23 PM, Jeroen Massar via NANOG wrote:
>>> Hi Dan,
>>>
>>> Hope the rest of the world is treating you decently!
>>>
>>> There are a lot of bits and bobs that one has to get right for mail to flow, amongst which:
>>>
>>>   - IP -> PTR lookup -> that hostname lookup, and match to IP again
>>>     (https://en.wikipedia.org/wiki/Forward-confirmed_reverse_DNS)
>>>   - SPF
>>>   - DKIM
>>>   - DMARC
>>>   - ARC (for mailinglists)
>> Seriously spend zero time on ARC. It doesn't work as advertised... [snip, see below]
> Unless one works at the large ESPs, hard to tell what they really care about and verify.
>
> Google at least adds ARC headers in Gmail, and did the editing of RFC8617.

ARC resolves into a previously unsolved problem: reputation. You could 
do reputation with plain old DKIM too, so I don't see why changing the 
name of the header changes anything on the ground. And nobody could give 
me an answer of why signing previous Authentication-Results is useful 
for toward that end. It's just more magical thinking.

Thank goodness it's an experimental RFC so it can go the way of the dodo.

Mike