Implementing anti-abuse techniques on ISP networks....

Andy Pitts andy at
Thu Aug 7 07:06:04 UTC 1997

> From owner-nanog at Wed Aug  6 19:10 EDT 1997
> Date: Wed, 6 Aug 1997 19:09:15 -0400 (EDT)
> From: Jon Lewis <jlewis at>
> To: Andy Pitts <andy at>
> cc: nanog at
> Subject: Re: Implementing anti-abuse techniques on ISP networks....
> MIME-Version: 1.0
> On Wed, 6 Aug 1997, Andy Pitts wrote:
> > I too, am a small Internet Service Provider, and I too, don't want
> > to block sites that my users may want to access.  But there seems
> > to be a few domains that do nothing but generate spam.  Am I not
> > providing a service to my users if I prevent them from being
> > smothered with spam from those sites?
> The issue is that there are ISPs that have filters such that their dialup
> customers cannot talk to port 25/tcp of systems elsewhere on the net.
> Customers have to use the provider's SMTP servers.  The question is, is
> this a good thing?  I don't think anyone would argue against UUNet and PSI
> doing this with the * dialups or the *
> would you do this on your own network?
> I've blocked 4 /16's and 12 /24's from talking
> directly to FDT's mail servers.  Unfortunately, most of the junk from PSI
> is relayed through other sites anyway.

I'm not blocking anyone from port 25, *but* I have installed the ruleset
in out sendmail to make it reject any mail that does not originale or
terminate in our domain.  This put a halt to the rash or relaying problems
we had some months ago, but down not affect our users in any way.

Andy Pitts                 : "Knowledge is a deadly friend
andy at         :  When no one sets the rules."        :        --King Crimson--

More information about the NANOG mailing list