get https://sandbox.datamotion.com/SecureMessagingApi/Message/Inbox/Unread
This method returns message summaries for all unread messages in the user's Inbox.
A session key must be submitted via the X-Session-Key header.
The request body should be left empty.
Include "?After={LastMessageIDReceived}" to specify the last message ID received to receive only messages created since the ID reference.
A successful transaction will receive a 200 status code.