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

John R Levine <johnl@taugh.com> Mon, 28 September 2020 22:44 UTC

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Date: 28 Sep 2020 18:44:31 -0400
Message-ID: <1cdaa0a2-74eb-d7ea-ede7-df3e41c82bd@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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> (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".

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