Milter-greylist

Tere.
>
> The URL in the message is always different but always resolves to the 
> same IP. That's a good basis for filtering...
>
>   
First You have to receive and parse message to find, does it include 
this url and later You can blacklist the sender's ip address, which is 
is always different.

Doing this, doesn't actually give You any relief, as in You cannot 
reject message in helo status.

-- 
Sysadmin