If you refer back to the table in the Enrichment section, you may have been intrigued by the Brokered property type. Messages that flow through bridges received from Service Bus are based on the Service Bus BrokeredMessage type (see http://msdn.microsoft.com/en-us/library/microsoft.servicebus.messaging.brokeredmessage.aspx for more details). This class provides a number of properties that are exposed in BizTalk Services such as CorrelationId, MessageId, and SessionId. What is really interesting about this is that when you are using the Service Bus Queue or Topic destination, properties you create in the bridge (any property, not just brokered properties) or properties set on received messages when Service Bus is the source are not just accessible inside the bridge, but outside of it as well. This is very useful for passing state from BizTalk Services to a downstream application consuming messages from a queue as that application will be able to see the properties you set...