Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321

Mark Andrews <marka@isc.org> Mon, 28 September 2020 23:11 UTC

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From: Mark Andrews <marka@isc.org>
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Date: Tue, 29 Sep 2020 09:11:20 +1000
Cc: Keith Moore <moore@network-heretics.com>, ietf-smtp@ietf.org
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To: John R Levine <johnl@taugh.com>
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Subject: Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321
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> On 29 Sep 2020, at 08:44, John R Levine <johnl@taugh.com> wrote:
> 
>> (There are already some IPv6 only ISPs and I expect this will become more viable over time.   Should they have to set up IPv4 tunnels or ALGs for their "legitimate" customers so those customers can still send email to IPv4 servers?)
> 
> No, they need a fixed IPv4 address with an MX so people on IPv4 servers can send mail *to* them.  As we've said a few dozen times already, one mail server on one IPv4 address can handle a whole lot of mail for a whole lot of people, both inbound and outbound.
> 
> The usual word for one-way mail to which one cannot reply is "spam”.

And if you have a IPv6 address that is reachable it is not “spam”.  Out bound address do not have to
match in bound addresses.  Remember this is delivering email to legacy addresses who may well end up
having a smart dual-stacked host for outbound traffic to workaround not having IPv6.

> Regards,
> John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
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Mark Andrews, ISC
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PHONE: +61 2 9871 4742              INTERNET: marka@isc.org