When a message is received by BizTalk, it is received via an Adapter; always. Adapters are the endpoints of any BizTalk system. They are the points of contact to the outside world; the gateways if you will, into the realm that is BizTalk. These endpoints could be File, HTTP, DB2, or any of the dozens of transports supported by BizTalk out of the box.
Upon arrival, all messages go to the Message Box, but to get there they must follow a specific sequence. The following is the list of actors involved in receiving a message listed in the order in which they process the message:
This flow is depicted in the following figure:
Before we discuss the Message ...