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Re: blocking port 25 at the border?
From: Mark Borrie <mark.borrie () OTAGO AC NZ>
Date: Fri, 24 Aug 2007 09:30:40 +1200

We have managed port 25 at the border for about 8 years. Only central
mailhubs are visible from outside. No local systems can send out on 25.

All mail domains are centrally registered and MXed to the incoming hubs,
which then route mail onto the mail servers.  Registered services smart
relay outgoing mail to the outwards hub service. Local clients must use
an on campus smtp host.

We initially set this up to stop open relays and other problems with
unpatched sendmail servers. Now virus and spam management are the prime
drivers. Interestingly, we are not seeing any impact from the Storm
worm. Our spam system must be catching the majority of the incoming and
we are not seeing locally infected systems (they could be there but they
cant send out and are probably trying to send directly anyway).


Bob Bayn wrote:
Do you regulate port 25 at the border?
If so, what is your procedure for allowing an exception
(for a legit email server)?
What administrative approvals were required at your
institution before you could regulate port 25?

Bob Bayn
IT Security Team
Utah State University
Logan, UT

Mark Borrie
Information Security Manager,
Information Technology Services, University of Otago,
Dunedin, N.Z.
Ph +64 3 479-8395, Fax +64 3 479-5080, Mobile +64 27 609-6409

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