[Mimedefang] OT: DNS sanity check

[John Rudd]

Jeff Rife wrote:
> On 4 Jul 2007 at 20:18, John Rudd wrote:

>> The false positive rate isn't based solely on rejections, it's based on 
>> things which triggered the Botnet rule.
> 
> You misunderstand.
> 
> Look at the messages that are being rejected solely because of the 
> extra 5 points you score for bad DNS.  I'm willing to bet that this is 
> a very small number of messages.

It's not.  Further, it means that the message had to be both spammy 
enough to score a 5 on its own, AND come from a host with poorly managed 
DNS.  That really does narrow down the field.

> Second, it's very likely that that in that small number of messages, 
> the the number of false positives is rather high, simply because the 
> total number of messages is small and the primary reason for rejection 
> has a *huge* false positive rate.

I can't speak for the internet as a whole, but it does NOT have a huge 
false positive rate.  It has a _tiny_ false positive rate.  Most 
legitimate outbound email servers do appear to have their DNS properly 
configured.  The ones who don't actually appear to be a small minority 
(from where I sit, and from where most of the users of my plugin report).