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

John Levine <johnl@taugh.com> Sun, 04 October 2020 19:24 UTC

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Cleverness: some
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Originator: johnl@iecc.com (John Levine)
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Subject: Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321
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In article <945d2baf-c5a9-fb9e-4563-93dff1824102@network-heretics.com>om>,
Keith Moore  <moore@network-heretics.com> wrote:
>Thanks for providing a list, though I wonder if this is the same as the 
>list that John referred to.

It's close enough.

>I do suspect that the list could use some updating.   For example:
>
>On 10/4/20 1:52 PM, Richard Clayton wrote:
>> For the next few years however:
>>
>> *  Use a static IPv4 address for your email system
>
>IMO this should change to support the reality that IPv4 addresses are 
>getting scarcer by the day, especially in some parts of the world.  

It's true, if you want a /16, you have to pay a lot of money for it.
On the other hand, you can rent a VPS with a unique public IPv4
address from any of a zillion places for a few dollars a month, so
"scarce" is a matter of perception.

Keeping in mind that the point of a standard is to interoperate, I
think it would be a good idea to offer advice that actually helps, you
know, to interoperate. The reality is that if you send mail from a
static address with matching forward and reverse DNS that doesn't look
generic and EHLO as that DNS name, you'll have a lot more success
getting your mail delivered than otherwise. (That's equally true for
IPv6, of course.) It'd be an a self-inflicited injury for us to tell
people otherwise.

-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly