anyone figure out how to make a content filter domains with passing spf results?

For example amazon.com uses spf. But they email from tons of addresses and much of their email get's dinged by the spam filter. I'm thinking i'd like to set up a rule that does nothing if mail is from a list of domains that use spf and they come with valid spf records. Then the next rule would be to junk anythign from those domains.

Anythign that is valid would hit the first rule and stop. Anything that is spoofed from those domains would get booted.

Any ideas?