Milter-greylist

Hi

I use sendmail, milter-greylist and mimedefang+spamassassin.

I'm getting lots of distributed dictionary attacks. I've read that
greylisting based on DCC will help. Is there any way to do this in
milter-greylist?

One idea I have is to add the triple from the DCC-positive message to
MG's database like this:
# echo "add addr $RelayIP from $Sender rcpt $Recip date $(date +%s)"  |
nc -s $myIP -w5 localhost 5252
(I could do this in mimedefang by checking the header that MG adds to
the message.)

But I think I should really greylist the relay itself. Is there a way to
greylist a relay (ignoring the sender and recipient)?

Is there any way to tell MG to greylist the relay and defer? 

TIA

Mark