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

John R Levine <johnl@taugh.com> Mon, 28 September 2020 22:41 UTC

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Date: 28 Sep 2020 18:41:14 -0400
Message-ID: <f4515ae9-edcb-8f89-7fd1-a02fe945a7f9@taugh.com>
From: "John R Levine" <johnl@taugh.com>
To: "Keith Moore" <moore@network-heretics.com>, ietf-smtp@ietf.org
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References: <20200928221602.046CE22A35B3@ary.qy> <9d36f20f-3652-6b4e-b7a6-4a4b7d6fcd66@network-heretics.com>
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Subject: Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321
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>> You appear to be saying there will be mail systems that need to send
>> mail to IPv4 systems, but will not have an IPv4 mail server so the
>> recipients can't reply to them.  Really?
>
> No, I'm saying that when IPv4 starts going away, there will be more and more 
> systems needing to send mail via NAT to such that client and server ends of 
> the connection have different address types.

Um, not to belabor the obvious, but I presume you know that to send 
someone mail, their domain needs to publish an MX record that points to a 
host with an A or AAAA record.

Could you explain in detail how I am supposed to send mail to people whose 
mail servers are stuck behind a NAT64 without a fixed public address?

Alternatively, it sounds like you're confusing submission and SMTP relay 
again.  We all agree that you don't need to verify IPs or anything like 
that for submission since submit clients identify themselves with AUTH.

Regards,
John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly