I have greylistd installed (on Debian with exim) and noticed last monday (March 6th) that Google has something like 26 outgoing SMTP servers for gmail. That doesn't work well with greylistd, though. So I added "64.233" to the whitehosts list. Not sure if that's the right thing to do or not, though. I'm not wildly excited about adding items to the whitehosts list.