[Mimedefang] the right place to put greylist check?

[Cahya Wirawan]

first I have to say that greylist is fantastic, I am testing
it since 2 days with our old domain address that is not used again but 
it still gets alot of mail traffic and almost all of them are spams.
This domain got 38000 email hits and tempfailed, but only 200 of them were 
back again, 170 of 200 were corectly detected as spam, 27 were hams and only 3 
spams were undetected . also less than 0.5% of spams attemp will
be back again , and if this 38000 tempfailed email hits are really spams
attempt, I can also say that my spam detection rate (with only 3 false
negativ) is bigger than 99.9%. This number is impossible if I use
only Spamassassin, no matter how smart it is. my spam detection rate
till now is about 90% (with old SA version), and geting worse since last 
few months.
 
So, my question is, where is the best place to put greylist in mimedefang.
At the moment I put greylist check in filter_recipient, it is now very
effectiv and very cheap since it saves also alot of bandwith, but I think   
if everyone use greylist before SA check the email, the effectivness of
dcc,razor or pyzor will suffer because there will be much less spams
tested by SA and therefore less automatic spam reports to the server.
How about your greylist implementation? do you use greylist check in
filter_end right after SA check and before exiting from the function?
is it save to say tempfail to the sender if they send already the data?

thanks,
cahya.