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

Sam Varshavchik <> Sun, 27 September 2020 13:01 UTC

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From: Sam Varshavchik <>
Date: Sun, 27 Sep 2020 09:01:36 -0400
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Subject: Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321
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Keith Moore writes:

> the fact that it works as a spam filter today seems like mere circumstance  
> or accident; I don't see any inherent reason that it will be a reliable spam  
> filter going into the future.   Spammers do learn, if slowly, so if they  
> have to learn to make sure their EHLO arguments match their source IP  
> addresses, they'll do that.   In the long term, I don't think this check  
> helps anything.

Yes, I agree. Domain validation is not mainstream, but it is being use in  
practice, just enough to fall under the radar stream. If for any reason –  
whether explicitly blessed in an RFC or for any other reason – it becomes  
more prevalent then spam generators will certainly adopt.

But at least right now it is a very effective filter. Like I wrote, this is  
really against my self-interest to bring more awareness to it.