SDK thats processing the event. Will always be 'botbuilder'.
The original source of the event (i.e. 'facebook', 'skype', 'slack', etc.)
The original event in the sources native schema. For outgoing messages can be used to pass source specific event data like custom attachments.
Defines type of event. Should be 'message' for an IMessage.
For incoming messages this is the user that sent the message. By default this is a copy of address.user but you can configure your bot with a lookupUser function that lets map the incoming user to an internal user id.
Address routing information for the event. Save this field to external storage somewhere to later compose a proactive message to the user.