Milter-greylist

I've been having a lot of multiple attempt spam that's coming from 
domain names that have been created in the last 2 months. 

Is there any way to look up a domain name to see when the name was 
created?  Whois services will only let you look up a few names before 
blocking you.

I'm thinking of making either a patch for milter-greylist or else a new 
milter to block domains that have been created within a configurable 
time period.  The theory is that the domain names will be dropped and/or 
the ips will be blacklisted before the end of your expiry period.  
Legitimate new domains will have to either wait or be white listed. 

Does milter-greylist deal with this issue already somehow?  Does anybody 
know of any other solution to this problem?  I think that spammers are 
getting more and more keen to the greylisting technique, and finding 
various workarounds.  I have large and ever increasing personal 
blacklist.  I think 90% of it involves recently created domains, though. 


Thanks.