Discussion:
Most amusing broken anti-spam technique of the week
(too old to reply)
John R. Levine
2013-03-18 17:35:28 UTC
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This guy's system has a swell anti-spam technique that checks all of the
sender's MX hosts for validity, where validity apparently means having an
A record. A quick check of mail6.iecc.com will reveal why it doesn't have
an A record, and why this complaint is particularly silly.

R's,
John

Diagnostic: 2001:06b0:0008:0002:0000:0000:0000:0203 does not like recipient. Remote host said: 554 5.7.1 Sorry; <asrg-owner+M112=pettai=***@lists.gurus.org> has an invalid MX record: MX Record: mail6.iecc.com does not resolve. Giving up on 2001:06b0:0008:0002:0000:0000:0000:0203.
Jose-Marcio Martins
2013-03-18 19:57:16 UTC
Permalink
Post by John R. Levine
This guy's system has a swell anti-spam technique that checks all of the
sender's MX hosts for validity, where validity apparently means having
an A record. A quick check of mail6.iecc.com will reveal why it doesn't
have an A record, and why this complaint is particularly silly.
Well, it's not me...

Well, the sender email address is ***@lists.gurus.org.

So, it's not a bad idea to check if the message can be answered. So
let's check MXs for domain lists.gurus.org :

lists.gurus.org. 7200 IN MX 100 nolist.services.net.
lists.gurus.org. 7200 IN MX 20 mail1.iecc.com.
lists.gurus.org. 7200 IN MX 20 mail6.iecc.com.

nolist.services.net and mail1.iecc.com has A record, but not mail6.
mail6 has a AAAA record.

So, the message can be answered in both IPv4 and IPv6.

Interesting configuration...

What's crazy here is that he checks only IPv4, MXs and not IPv6, but his
"mail box" seems to handle (or have) IPv6 addresses but not IPv6 SMTP
traffic.
Post by John R. Levine
R's,
John
Diagnostic: 2001:06b0:0008:0002:0000:0000:0000:0203 does not like
recipient. Remote host said: 554 5.7.1 Sorry;
record: MX Record: mail6.iecc.com does not resolve. Giving up on
2001:06b0:0008:0002:0000:0000:0000:0203.
--
Envoyé de ma machine à écrire.
---------------------------------------------------------------
Spam : Classement statistique de messages électroniques -
Une approche pragmatique
Chez Amazon.fr : http://amzn.to/LEscRu ou http://bit.ly/SpamJM
---------------------------------------------------------------
Jose Marcio MARTINS DA CRUZ http://www.j-chkmail.org
Ecole des Mines de Paris http://bit.ly/SpamJM
60, bd Saint Michel 75272 - PARIS CEDEX 06
mailto:Jose-***@mines-paristech.fr
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