• An Important Note
• What Is An Envelope
• Delivery Process For An Envelope
• Passing An Envelope To A Mbox
• msg_type For An Envelope
• Extraction Of Envelope's Payload
• Envelope's Hook
• Multiple Invocations Of Hooks
• Envelope And Multithreading
• Envelope And Message Limits
• Nested Envelopes
• Ready To Use Envelopes