[Dshield] DNS MX record block question

Tom Laermans tom.laermans at powersource.cx
Sat Sep 6 02:49:56 GMT 2003

At 03:24 06-09-2003, you wrote:
>Some mailservers have the option to configure them not to accept mail from
>incorrectly assigned rdns entries. In other words, your server gets a mail
>from someone at somewhere.com, looks up the IP it's receiving it from, and
>discovers that the IP is somehost.somewhereelse.com so it rejects it. This
>is a perfectly valid thing to do... since Jon's already mentioned RFC's, I
>believe there's also an (widely ignored) RFC which states that a sending
>mailserver must have a valid rdns record pointing to the domain it's coming

I think you are confused here, and you mean checking the rdns of the 
HELO/EHLO of the mailserver, not the domain itself. Otherwise we're back in 
the stoneage with 1 ip per domainname.


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