Re: smtp redirection

[Aaron Childs <aaron () WSC MA EDU>]

John,

  We just implemented an anti-spam appliance as well (Risk Filter by
Surf Control).  We also redirect email using MX records however as a
preventative measure (and for security reasons) I setup an access-list
in our router to have all email flow through the appliance.

 

Aaron

 

------------

Aaron Childs

Assistant Director, Networking

Westfield State College

http://www.wsc.ma.edu/it/

  _____  

From: The EDUCAUSE Security Discussion Group Listserv
[mailto:SECURITY () LISTSERV EDUCAUSE EDU] On Behalf Of John
Sent: Tuesday, May 10, 2005 3:32 PM
To: SECURITY () LISTSERV EDUCAUSE EDU
Subject: [SECURITY] smtp redirection

 

Greetings All,

 

We are redirecting smtp traffic inbound to some campus mail servers via
MX records in our DNS to an anti-spam appliance (Bluecat Meridius) and
find some email circumvents the appliance apparently by using DNS IP
lookup for host resolution and not using MX records to send mail to mail
servers on our campus. The vendor recommends blocking inbound port 25 to
the campus mail servers from the internet. I favor this approach.
However the mail folks are concerned that some legitimate email may be
dropped this way.

 

For those of you who redirect email to an anti-spam device; how are you
doing this redirection and how are you dealing with the spammers who
circumvent the MX record approach?

 

Before changing MX records I set a route map on a router to redirect
smtp traffic to the Meridius but the IP destination headers did not have
the Meridius address so the appliance dropped the traffic. We run a
public class B and do not do NAT.

 

I very much appreciate your solutions, ideas, critiques and war stories.

 

Cheers,

 

John Garner

jgarner () sfasu edu

Stephen F. Austin State U

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