North American Network Operators Group

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Re: SMTP authentication for broadband providers

  • From: Suresh Ramasubramanian
  • Date: Wed Feb 11 20:50:39 2004

Will Yardley wrote:

My understanding is that in most cases, providers are blocking port 25
outbound to prevent direct to MX spamming from their customers' machines
If you do that, please put in a corresponding ACL to block port 25 inbound _and_ outbound.

Otherwise, you just might get bitten by something like spoofed source routing, as several providers have found out in the past.