Thought it would be nice to post about something that works instead something not working. I've been using postgrey for a few years now and you can forget how effective it is after a while.
Half a week ago I was screwing around with my postfix main.cf file and unwittingly did something that put postgrey out of commission, although I didn't realize it at the time. For several days after I've been getting a shocking number of clients telling me they were getting way more more spam. It appeared to me everything was working on my end and didn't really know what to make of it. Btw, my own mail is not handled through my server. I kept looking into this because there were just too many complaints to ignore. Low and behold I discovered Greylisting not working and corrected the main.cf file and everything went right back to normal.
I don't tell clients about my use of Greylisting any more than I have to. Everyone tends to think they need to get the mail the second it's sent and freak out at the thought of the mail being rejected that first time. But I'll tell you, the clients I took the time to explain what happened don't mind me using Greylisting now!