Subject: Re: [Asrg] MXs Used As Authentication - Why RMX?

From: "Alan DeKok" <[email-masked]>
Date: Mon, 25 Aug 2003 11:58:17 -0400

Bill Cole <[email-masked]> wrote:
> It is not what happens in the real world. For sites handling 
> significant mail volume, outbound mail and inbound mail are large 
> enough and different enough in their ideal system design that it 
> makes sense to have them handled by different systems.

  Further, anecdotal evidence suggests that the simple existence of
outgoing SMTP servers means that they will be targeted by spammers.

  That is, mailing list archives contain IP's of outgoing SMTP
servers, and spammers troll the net looking for such IP's.  When
found, those IP's are hit with delivery attempts for that domain,
relay attempts, and other nonsense.

  It's been suggested that outgoing SMTP servers should be in an
entirely different address range than incoming servers, and that those
outgoing servers shouldn't accept ANY traffic other than what they
originate.  No SMTP, no ICMP, nothing at all.

  Similarly, I'm seeing 1000's of delivery attempts a day for a
domain, to an IP which hasn't been the MX for that domain for years.
Spammers really are that desperate.

  Alan DeKok.

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---

From: Bart Schaefer <[email-masked]>
Date: Mon, 25 Aug 2003 18:51:36 +0000

On Aug 25, 11:58am, Alan DeKok wrote:
} Subject: Re: [Asrg] MXs Used As Authentication - Why RMX?
}
}   It's been suggested that outgoing SMTP servers should be in an
} entirely different address range than incoming servers, and that those
} outgoing servers shouldn't accept ANY traffic other than what they
} originate.  No SMTP, no ICMP, nothing at all.

Servers configured that way may find that they are not able to send
mail to aol.com addresses.  AOL now periodically tests IPs from which it
recieves inbound mail to determine whether they are open relays.  My
experience has been that if those IPs simply refuse inbound SMTP, they
get put on AOL's blacklist; to pass AOL's open relay test, the server
must both accept an SMTP connection, and then refuse to transmit.