how to stop using *telnet <domain> 25*

[Gary]

On Sat, Jan 24, 2004 at 01:21:40PM -0500 or thereabouts, David A. Bandel wrote:
 <snip>  
> > If they are using port 25, and you have an MTA running, sendmail,
> > postfix, or qmail.  You should set your MTA to allow use for only your
> > existing internal IP range, and you will not have this problem.. They
> > will not be able to send mail period. 
> > 
> > In short, you have not properly closed down your MTA, and you are an
> > open relay. 
> 
> Not exactly.  If the addresses the spammer is sending to is on that mail
> server, then of course it has to accept the mail (not 100% true, you can
> block IPs that don't reverse or resolve as mail servers -- I use
> milter-sender to do this).

Is that the problem here, that a spammer is sending to a known address? Or
is it that a spammer is trying to use his MTA to send spam outbound?  As
mentioned, this was unclear to me.. 

Blocking IP ranges that have no reverse DNS is one of the first lines of
defense I use on my servers with qmail, in the tcp.smtp file, one line,
blocks them all. 


-- 
Gary