You could do this via LDAP acceptance queries. Acceptance queries allow for the envelope sender address to be part of the query. You'd then need a special LDAP server that could implement your policy rather than being a simple directory.
But I have to agree with bvanzant, it's not a big deal to reject these via a message filter in the work queue. Unless your MGA is overloaded and rejecting these messages would constitute a huge savings, it's just not worth the effort. Just bounce them (so Yahoo gets the message), and be done with it.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...