Whitelist Domains for Email Delivery in Google Apps

As a Google Apps Certified Trainer, I get the opportunity to do a series of short screencast tutorials.  This is the first in a series of four that I've signed up to create.  In just over a minute, this video walks through the steps of restricting email delivery for an organization in your domain and adding a whitelist of domains that can send emails to and receive emails from that organization.  I hope you enjoy.