Those are basically the semantics of SMTP delivery. Come to think of it, that protocol could make more sense than HTTP for asynchronously messaging entities. I

Those are basically the semantics of SMTP delivery. Come to think of it, that protocol could make more sense than HTTP for asynchronously messaging entities. I love the simplicity of webhooks, but sometimes it's nice to abstract away the redelivery mechanism without having to set up one's own broker. FWIW, that's the underlying protocol used in BlueButtonPlus[0], the proposed method for exchanging healthcare information. [0] http://bluebuttonplus.org/transmit-using-direct.html http://bluebuttonplus.org/transmit-using-direct.html