I turned on greylisting last week and it makes a very useful and noticeable reduction in spam - so thanks for that!
Q: are there any greylist specific logs/stats/reports or config options anywhere?
Well, I’ll offer that Virtualmin Pro comes with a number of nifty graphing capabilities.
You could tell it that you wanted to see the number of email messages, spams, and viruses it’s seeing per minute – over the last week.
And you’d see lots and lots of spams until you installed the greylisting, and which point that line would shoot down. It would look all impressive and stuff 
There are other graphing tools out there – I haven’t dealt with them recently, but poking around on Google, I see things like Mailgraph, which uses rrdtool to generate graphs.
-Eric
Hi Eric
yea I got the regular VM stats stuff - and you’re right: spam related graphs do show significant reductions in spam.
I’d wondered if there was anything within the vm gui that turned out pretty looking postgrey specific reports, maybe using postgreyreport / postgrey.db? but i cant find it.
I came across cli options in this centos howto
http://wiki.centos.org/HowTos/postgrey
To get the top 20 sources getting greylisted out:
cat /var/log/maillog | postgreyreport | awk ‘{print $1}’ | sort | uniq -c | sort -nr | head -n20
To get a list of the top 20 email address that the greylisted sources are sending email to:
cat /var/log/maillog | postgreyreport | awk ‘{print $4}’ | sort | uniq -c | sort -nr | head -n20