Re: [DNSOP] I-D Action: draft-ietf-dnsop-isp-ip6rdns-03.txt

Lee Howard <> Fri, 12 May 2017 12:21 UTC

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Date: Fri, 12 May 2017 08:16:42 -0400
From: Lee Howard <>
To: Paul Vixie <>, John Levine <>
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Thread-Topic: [DNSOP] I-D Action: draft-ietf-dnsop-isp-ip6rdns-03.txt
References: <20170511165852.34338.qmail@ary.lan> <>
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Subject: Re: [DNSOP] I-D Action: draft-ietf-dnsop-isp-ip6rdns-03.txt
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On 5/11/17, 1:28 PM, "DNSOP on behalf of Paul Vixie"
< on behalf of> wrote:

>John Levine wrote:
>>>>> In my experience, without reverse DNS it is essentially impossible
>>>>>to have
>>>>> mail delivered to the internet at large.
>>>> Yes.
>>> since this isn't an ideal or intended state of affairs, let's consider
>>> the size and shape of the box, not just what's in there.
>> What would be the operational advantage of accepting mail from IPv6
>> too lame to set up rDNS?
>we will never know, because every v6 end system will have a ptr, either
>naturally, or machine-generated for it, because v6 providers will not
>want their rank-and-file v6 endsystems to be excluded from important
>activities such as transmitting e-mail.

If ³v6 provider² includes ³residential ISP² (the topic and audience for
this draft), then the inability to transmit email is by design.
That is: ISPs commonly prevent residential users from sending email (by
default). They say this in their Terms of Service, they block port 25, and
they don¹t publish PTRs. This is consistent with recommendations by
M3AAWG[1] and BITAG[2], for instance.


I¹m pretty sure this is a consensus position.

>the operational advantage of not having ptr's for rank and file end
>systems is much easier to explain, except to v6 endsystem providers.

People who run mail servers generally understand these limitations. The
BITAG paper does recommend clear disclosure and methods to opt-out. Makes
sense to me: I want a human decided they want their system to send mail,
not a bot.