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

Dave Crocker <> Sun, 27 September 2020 16:29 UTC

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To: Keith Moore <>
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From: Dave Crocker <>
Organization: Brandenburg InternetWorking
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Date: Sun, 27 Sep 2020 09:29:24 -0700
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Subject: Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321
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On 9/27/2020 8:33 AM, Keith Moore wrote:
> On 9/27/20 11:04 AM, John R Levine wrote:
> Anything that comes from a dynamic or NAT pool is invariably spam from 
> a botnet.
> No, because nobody is looking that closely.   It's basically just 
> prejudice that assumes that "legitimate" senders have static IP 
> addresses, delegation of the corresponding zone in, and 
> the knowledge to populate the PTR records.

John L. has been correctly summarizing what members of M3AAWG have been 
quite consistent about, for many years.  It is part of the reason that 
running a legitimate mail server on the open Internet, these days, 
requires a significant amount of knowledge about the rather elaborate 
set of expected configuration and procedure.

Properly registering the domain name and the IP address, forward and 
backwards, has been one of the more basic and practical requirements for 
at least 10 years, that I know of, but probably a lot longer.

As for 'prejudice', I encourage folk to spend some time around the 
anti-abuse industry and learn more about how it operates, since it takes 
a 95% spam level for incoming mail and brings in down to a tiny percent.


Dave Crocker
Brandenburg InternetWorking