Milter-greylist

On Thu, Sep 07, 2006 at 09:30:25AM -0400, Chris Hoogendyk wrote:
> I've been getting more stock spam lately. Every time I check full
> headers, I see the greylist header indicating that the message was
> delayed. So they are resending. What I'm seeing getting through is
> almost entirely stock spam (stock alerts, investment, etc.).

If you increase the delay, they will give up. 
Handling resends needs resources. The spammer midly care, since he
is not paying for the CPU, memory, and disk space of hijacked machines.
On the other hand, this free resource is not infinite. If the machine 
sends 100 message per second to servers with a delay of 12 hours, the 
resend queue will grow up exhausting available resources.

But it is not possible to have a delay of 12 hours for everyone. This is
why I indtroduced DNSRBL and per-ACL delays in milter-greylist. You can
now have different delays depending on the sender reputation. Machines on
dynamic IP pools are not likely to be real SMTP servers, so we can 
affore a much higher delay for them. And that seems to do the trick.

-- 
Emmanuel Dreyfus
manu@...