[unisog] Port 25 blocking - on the

Chris Crowley ccrowley at tulane.edu
Fri Apr 29 21:52:01 GMT 2005

In addition to some of the other mentioned strategies, we rate-limit
systems on our network sending e-mail through our SMTP server -- for
most of the network, systems are prevented from using tcp port 25 to
anywhere outside of the network.

Using a customized DCC installation, once a system has sent mail to more
than "x" recipients per hour, the system is prohibited from sending any
more e-mail.

So, if an infected or open relay system attempts to send lots of mail,
it gets stopped, and flagged as a problem.  There is a procedure in
place to request exception from the limit for internal bulk mailing.

Christopher Crowley
ccrowley at tulane.edu
(504) 314-2535
Network Administrator
Technology Services
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