For a while now I’ve been thinking about writing a post that documents all the gritty details of how the BizTalk messaging engine hooks into the WCF stack in the various WCF adapters. Now I don’t have to as Paolo Salvatori has done a stunning job: http://blogs.msdn.com/paolos/archive/2009/11/17/customizing-and-extending-the-biztalk-wcf-adapters.aspx Well done mate. This is by far the best explanation of how the BizTalk WCF adapter stack actually works. It should be in the documentation!