Educause Security Discussion mailing list archives

Re: smtp redirection


From: Valdis Kletnieks <Valdis.Kletnieks () VT EDU>
Date: Tue, 10 May 2005 15:57:17 -0400

On Tue, 10 May 2005 14:32:09 CDT, John said:

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.

It's been *many* moons since anything except ratware failed to do MX handling
in some reasonable manner.  I mean, come *ON*, MX records were defined in RFC973.

Back in January 1986.

If your mail folks can identify a system *still* on the Internet that's running
software *so* old that it can't do MX, please let me know - as far as I know,
all systems that stored 6 6bit, 5 7-bit, or 4 9-bit characters in a 36-bit word
had long since boarded the Elven ships at the Grey Havens and passed into the
West, taking their magic and mystery with them.



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