If incoming, the author that sent the message, if the message was sent in a channel. If outgoing, undefined.
The contact that sent or received the message.
The unique identifier of the message. This can be used to lookup messages in the history. This identifier persists across sessions.
Whether the message was received or sent.
The timestamp of the message.
A Zello history image message. To retrieve the image data for the message, use the Zello#getImageDataForHistoryImageMessage method.