nanog mailing list archives

Re: SMTP Port Blocking: Success or Failure?


From: "Christopher L. Morrow" <christopher.morrow () mci com>
Date: Sun, 27 Feb 2005 05:48:09 +0000 (GMT)



On Sat, 26 Feb 2005, Claydon, Tom wrote:


We are considering filtering outbound SMTP traffic from our ISP
customers, except from our own mail servers, to help reduce the amount
of spam originating from our network. How successful/unsucessful has
implementing outbound SMTP filtering done in stopping or slowing down
spam from your network?

If you mean on Dial customers this sort of thing has been very helpful,
add (as the previous conversations on this have shown, outbound to the
dial user filters permitting source port 25 from your mail complex alone
as well.


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