Anti-spam SMTP mods

[Daniel Siemens]

SBC Yahoo DSL will set up reverse DNS for you if you ask them to do it. The first 3 levels of tech 
support have no idea what you are talking about it, but if you are persistent you will get it.   I 
have static IP, not dynamic ip though.    
 
You are running servers on dynamic connections?   Do you have any delays when you IP updates for 
DNS to correctly adjust?   Which Dynamic DNS provider are you using?   Are they any good?     
 
 
 

________________________________

From: owner-kclug at kclug.org on behalf of Jonathan Hutchins
Sent: Tue 3/9/2004 1:58 PM
To: kclug at kclug.org
Subject: Re: Anti-spam SMTP mods

On Tuesday March 9 2004 12:04 pm, Daniel Siemens wrote:

> If all admins would set up reverse DNS...

Not all can.  For instance, I can't unless I buy a commercial connection,
because reverse DNS gives a RR pool hostname.  It's bad enough that less than
competent admins are blocking all "dynamic" IP addresses like mine.

Blocking mail where there is _no_ valid reverse DNS is very effective.  I did
have that enabled, and when I had to un-block it (per my ISP's policies), the
mail that came in was 100% spam.  Some of that still gets by my beysian
filters for some reason.

I would recommend a combination of requiring that a reverse DNS exists, even
if it doesn't match the server name presented, and using other measures like
scoring mis-matched reverse DNS and dynamic IP addresses.