[exim] greylisting

Hi,

I'm somewhat new to Exim. I'm working on an Exim configuration for a mailhub design. I have a number of ACL's working fine on a test FreeBSD machine. However, I am still working on implementing greylisting. On the net I found 4 or 5 different approaches to greylisting, but I'm not sure what is the best practice. I'm interested in a simple but smart design. The production platform will ultimately be Suse, and we will have at least 2 redundant servers. I would appreciate any comments from people who have successfully implemented greylisting on any platform. Is the easiest approach to just write a simple custom perl script?

Thanks in advance for any suggestion,

Jeanne