How many people eat meat but don't consume milk in some form, whether that be directly or through cheese, ice cream, butter, etc? I'm guessing its a pretty small number.
I integrated and adminsiter a postfix / sa / clamd / courier system for about 10,000 domains (6 identical blades with local storage for the queues and Global File System GFS once they've been accepted).
SA gets about 95% accuracy on our system even at 5.0
I can also recommend enabling SPF and DKIM see http://www.openspf.org/
Wave bye bye to emails pretending to be sent from yourself to yourself or those annoying "your settings have changed, open this zip file" mails.
http://www.motogp.com/en/riders/profiles/julian+simon