Re: Most amusing broken anti-spam technique of the week

John R. Levine wrote:
> 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 [email protected].

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.

>
> R's,
> John
>
> Diagnostic: 2001:06b0:0008:0002:0000:0000:0000:0203 does not like
> recipient. Remote host said: 554 5.7.1 Sorry;
> <[email protected]> has an invalid MX
> record: MX Record: mail6.iecc.com does not resolve. Giving up on
> 2001:06b0:0008:0002:0000:0000:0000:0203.
>


-- 

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