North American Network Operators Group

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Re: SMTP Port Blocking: Success or Failure?

  • From: Ketil Froyn
  • Date: Sun Feb 27 08:20:05 2005

Quoting "Claydon, Tom" <[email protected]>:

> 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?

What about rate limiting SMTP traffic rather than blocking it? That could allow
legitimate use for most private customers, while preventing bulk traffic.

Capping the number of messages per customer in the ISP mail server would
probably also be a good idea, I hear more and more bulk traffic is being sent
through ISP mail servers.