The Exchange Server 2016 built on the similar architecture as in Exchange Server 2013, with one major change by removing the Client Access Server role. MS has removed Client Access Server role and introduced client access services to the Mailbox role. As a result, the Mailbox server role contains,
It might remind some of us the architecture in Exchange Server 2003, but with a FE role. However, we still need to wait and see the actual product and its capabilities.
As per the introductory note, it is underlining that MS is not compromising the backend infrastructure client connectivity security. Even by removing the CAS role, no clients would connect directly to the back-end endpoints on the Mailbox server; instead, clients connect client access services and are routed (via local or remote proxy) to the Mailbox server that hosts the active database that contains the user’s mailbox.
There are changes in the architecture of DAG as well. As usual, the building block concept is still valid, as the additional mailbox servers can be added to form HA unit with the following additional enhancements,
The following diagram from MS shows the client protocol connectivity.
This is not all, there are major other developments in the overall architecture, please follow the article from Microsoft Exchange Blog here. Happy reading.