Removed the Client Access server (CAS) role and added the client access services to the Mailbox role (Even without the CAS role) the system maintains loose coupling in terms of functionality, versioning, user partitioning and geographical affinity.
The Mailbox server role now:
Houses the logic to route protocol requests to the correct destination endpoint.
Hosts all of the components and/or protocols that process, render and store the data.
Can be added to a Database Availability Group (DAG), thereby forming a high availability unit that can be deployed in one or more datacenters. DAGs in Exchange Server 2016 do have a few specific enhancements:
Database Availability Group IP Addresses is no longer required when creating a DAG. By default, the failover cluster will be created without an administrative access point, as this is the recommended best practice.
Replay Lag Manager is enabled by default.
Lagged database copy play down can be delayed based on disk latency, thereby ensuring active users are not impacted.
Database failovers times are reduced by 33% when compared to Exchange Server 2013
Working with emails and documents has also greatly improved, with the help of side-by-side document viewing and editing. So basically you can now simultaneously see the email sent in OWA, your reply that you are currently writing and the document in read or edit mode!
Enabled by default. In addition, Exchange Server 2016 introduces per-user control over this connectivity model, as well as, the ability to control whether the protocol (and Outlook Anywhere) is advertised to external clients.
Support on operation systems:
Windows Server 2012
Windows Server 2012 R2
Windows Server “10”
Exchange Server 2016 will require:
Windows Server 2008 or later Active Directory servers.
Windows Server 2008 or higher Forest Functional Mode and Domain Functional Mode.