Milter-greylist

--- In milter-greylist@yahoogroups.com, manu@... wrote:
>
> I just realized that the reverse DNS is something out of control of the
> botnet spammer. 
> 
> Filtering on reverse DNS name with three 0-255 numbers sounds therefore
> a good idea. The drawback is that you will catch power users that send
> from their home machines, and SME using SMTP appliances.
> 
> You could send a permanent error with an URL on which you'd tell that
> you are okay to whitelist the IP on request. You can even do it
> automatically by a web form with a challenge to check the visitor is not
> a bot.
> 
> That looks efficient. I'll try it.

Instead of trying to parse all the formats used in reverse DNS
yourself, how about querying a blackhole list. There are several that
 specificly list dialup and broadband users IPs.

If we could query one or more blackhole lists and allow the results to
help decide if an IP is going to be greylisted and maybe modify the
length of time it's greylisted I think it'd help alot.