North American Network Operators Group

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Re: ingress SMTP

  • From: Simon Waters
  • Date: Wed Sep 03 13:24:47 2008

On Wednesday 03 September 2008 18:07:22 Stephen Sprunk wrote:
>
> When port 25 block was first instituted, several providers actually
> redirected connections to their own servers (with spam filters and/or
> rate limits) rather than blocking the port entirely.  This seems like a
> good compromise for port 25 in particular, provided you have the tools
> available to implement and support it properly.

It generated some very confused support calls here, where folks said I sent 
email to your server, and we had to tell them "no you didn't, you only 
thought you did".

Please if you are going to block it block it clearly and transparently.

On the other hand abuse by bots isn't restricted to SMTP, and I suspect ISPs 
would be better of long term having a way of spotting compromised/malicious 
hosts and dealing with them, than applying a sticky plaster to port 25. 
Indeed spewing on port 25 is probably a good sign you need to apply said 
system.