Milter-greylist

I've been requested by some people to have milter greylist automatically 
add address book names to its whitelist.  Since I don't have access to 
client address books on my server, I'm planning on scanning IMAP 
databases for addresses.  Any address that appears in a sent folder or 
in a receipt folder other than Junk for longer than a few days will get 
added to a whitelist in greylist.conf. 

Is there an easier way to do this?

Also, I currently don't use SPF whitelisting.  Maybe that will waylay 
the need for complex whitelisting. I want to use it, but haven't gotten 
to updating yet.  I've read that it only has 10% to 20% adoption, so it 
may not give me such a big benefit, other than being part of the cause I 
guess.

Thanks.