Check smtp server sender address in internal local domain

In Domino there is an option in configuration document “Verify that local domain recipients exist in the Domino Directory” for SMTP. That’s great and work well.But in local doamin (Internal) someone can send message from fake address to existing address.

How can i verify that local domain SENDER (“Mail From:” field) exist in the Domino Directory, when domino server receive SMTP message.