Messaging is the core functionality provided within BizTalk Server. On a very basic level, it is the plumbing that moves messages from one location to another. A number of different parts or objects make up this plumbing, taking actions at each step of a message’s path through BizTalk Server. Generally speaking, messaging objects can be split into two categories: receive and send. Figure 4-1 outlines the stages a message goes through as it is processed.