Policy-enforced TLS provides

Emerging regulations and best practices are encouraging companies to encrypt email messages that contain sensitive and confidential information. Policy-enforced TLS employs transport layer security to automatically encrypt email connections between businesses. Google Security service, powered by Postini, integrates strong TLS encryption with policy-based management so you can control and ensure which messages are delivered over encrypted connections.

Policy-enforced TLS provides

Enforced server-to-server encryption, prevents un-encrypted emails from being sent
Automatic processing, with no additional integration
Zero impact to recipient–does not require software or key installation
Secure communications with regular business partners without the cost of virtual private networks and leased lines
Simple administration via the Administrative Console