Google added a new feature “policy-enforced Transport Layer Security (TLS, RFC 2246)” into Google Apps to help you secure the transport of messages between domains with a simple point-and-click interface. With policy-enforced TLS, IT administrators can set up policies for securely sending and receiving mail between specific domains. The new functionality makes it easy for an IT admin to use the TLS standard for reliable, secure email delivery – with no hardware or software to add or maintain.

Full Article: Google Enterprise blog