North American Network Operators Group

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Re: SMTP Port Blocking: Success or Failure?

  • From: Christopher L. Morrow
  • Date: Sun Feb 27 00:50:53 2005

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.