The device that is sending the messages. The partner (e.g. AllScripts), if any, that is managing the sender. The device that is to receive the messages. Request an ReadReceipt, including any back and forth messages in either direction clarifying the reason or scheduling and requesting or providing additional information or alternative times. Request a ReadReceipt, including any back and forth messages in either direction requesting or providing additional information. The request typically includes preferences for a specific staff member, timing, etc. A sender-generated universally unique identifier that uniquely identifies this message. The date and time that the message was sent. This should be an absolute date time (UTC or including time zone offset). If omitted, the receiver should assume the current time.