Re: Getting open smtp servers fixed

[James Aldridge <]

Richard Kettlewell wrote:
> c) filter out all port 25 tcp connections from dialup customers unless
>    they are to yoru smarthost(s).
> 
> The spammer can still use the smarthost (much as if they were using an
> open relay, of course) but you by forcing all the mail through a
> single point the ISP can more easily detect the spammer early on.

By forcing all traffic through the ISP's SMTP server you also have the
opportunity to throttle the maximum rate of outgoing messages from customer
machines.  This may not stop spam completely but can greatly reduce its
impact on the world at large.  Legitimate customers, of course, should be
able to request an unthrottled SMTP connection.

James