Which of the following options is not available within a Secure Receipt Policy?

The Secure Receipt Policy is designed to manage how secure communications are handled and to provide assurance that messages are delivered securely and verified appropriately. The correct choice indicates a feature that doesn’t exist within this specific policy structure.

Enforcing TLS (Transport Layer Security) commonly ensures that emails are transmitted securely over the internet, but the option to "fall back to Secure Message" is not an inherent feature of the Secure Receipt Policy. Instead, the policy primarily focuses on aspects like sender authentication and notifying the sender when a recipient reads the message, enhancing accountability and security in the communication process.

Features like requiring sender authentication, tracking delivery status, and notifying upon read are logically consistent with the goals of a Secure Receipt Policy, as they either verify the sender’s identity or confirm the successful receipt and reading of the secure message. However, the idea of enforcing TLS with a fallback to another type of secure message does not align with the established features of this policy, as securing the transmission directly is outside its scope.