A new email system?

I'm looking for a system that will work with Gmail and do the following:
  • Make it easy to maintain a white list
  • Auto-respond to and forward every email from someone not on the white list
  • Bonus: the forward goes to to different address, depending on contents of email
(I realize I can accomplish the above with Gmail filters and the new canned responses. But maintainability is key. Editing the white list from from: -address is hard and seems like it likely (?) has a limit well below the hundreds I'd need.)

Does this exist? If so, @ev me.