An electronic mail system and method in which a message receiver creates an envelope containing envelope media data that is hidden with an embedding-and-extracting key. The message sender acquires the message receiver's envelope and, using an embedding-and-extracting key, embeds a secret message in the acquired envelope media data. The embedded envelope is sent to the message receiver, who extracts the secret message from the received embedded envelope using the same embedding-and-extracting key used to embed the data. As a result a secret message can be sent from the sender to the receiver without being eavesdropped on during the communication.