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

2020-09-27 00:22:45
In article 
<da460777-824b-1f13-be7c-32bfa9664d02(_at_)network-heretics(_dot_)com> you 
On 9/18/20 6:36 PM, Sam Varshavchik wrote:

Courier has an optional setting that can be enabled, that verifies 
that "the domain name argument in the EHLO command actually correspond 
to the IP address". I have it enabled. It's one of my most successful 
spam filters. ...

At some point in the past, this was _not_ a reliable spam filter. ...

I think you may be conflating SMTP and submission. For submission,
you're right, the EHLO argument is frequently some random name that a
computer thinks it has behind a couple of layers of NAT. For SMTP,
server to server, I agree with Sam that it is extremely rare for a
legit message to come from a host that doesn't know its name.


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