Exchange Web Services Architecture
Applications that use Exchange Web Services can access data store items. The applications can access these items locally or remotely by using a SOAP version 1.1 or version 1.2 message. SOAP is an XML-based protocol that is defined in the World Wide Web Consortium (W3C). The SOAP messages are sent between client and server, embedded in an HTTP 1.1 message. The HTTP 1.1 protocol is defined by RFC 2616.
Exchange Web Services is deployed with the Client Access server role. Microsoft Exchange Server 2010 clients connect to the computer that is running Exchange 2010 that has the Client Access server role installed in an Active Directory directory service site by using an HTTPS connection. If the target mailbox is in another Active Directory site, the source Client Access server creates an HTTPS connection to the target Client Access server. The target Client Access server obtains the information by communicating over MAPI to the Exchange server that has the Mailbox server role installed and then sends it back to the source Client Access server. If the target mailbox is in the same Active Directory site, the Client Access server uses MAPI to communicate with the Mailbox server to obtain the information. The Client Access server then provides the data back to the client.
When a client application requests information from the Exchange store, an XML request message that complies with the SOAP standard is created and sent to the Exchange server. When the Microsoft Exchange server receives the request, it verifies the credentials that are provided by the client and automatically parses the XML for the requested data. The server then builds a SOAP response that contains XML data that represents the requested strongly typed objects and their properties. The XML data is sent back to the client application in an HTTP response. The client application then deserializes the XML and uses the data to reform the strongly typed objects.
The following figure shows how a client application interacts with the Client Access server to access Exchange store information from the Mailbox server.