Milter-greylist

Hi,

since a few weeks I see a lot of delivery attempts on my mail servers to 
non-existent and existent addresses from hosts that are listed on the 
common blacklists like Spamhouse etc..

I see up to a hundred attempts on email addresses in a single 
connection. Milter-greylist correctly acknowledges these requests with a 
5xx, if the recipient exists:

551 5.7.1 Bad reputation - x4e3105c4.dyn.t-online.de [78.49.5.2] listed 
on too many DNS blacklists: ZEN BL_BARRACUDA BL_SORBS (blhit 6)
rcpt to: <lists@....>

The problem is that the sender keeps trying. For every address that 
exists a new BL lookup is generated.

Isn't it possible to terminate the connection on the server side as soon 
as a "racl blacklist list" hits?

Ciao!