Server role consolidationIn previous versions of Exchange, we had option to install the Client Access server role and the Mailbox server role on separate computers. In Exchange 2016, the Client Access server role is installed as part of the Mailbox server role. Client Access server role is not available as a separate installation option.A multi-role Exchange server architecture benefits:
Simplified hardware purchasing, maintenance and management of the Exchange servers.
Fewer physical Exchange servers resulting in less maintenance costs, less Exchange server licenses, and less rack/floor space, and power requirements.
Improved scalability. During a failure, the load on the remaining Exchange multi-role servers increases only incrementally, hence no adverse effect on other exchange functions.
Improved resiliency, because a multi-role Exchange server can survive a greater number of Client Access service failures.
Search improvements The local search instance is now can read data from the local mailbox database copy. Hence, no need for passive instances to perform indexing from their Active counterparts.
Office Online Server Preview for Outlook on the web document previewIn Exchange 2016, Outlook on the web uses Office Online Server Preview to provide rich preview and editing capabilities for documents. You need to deploy Office Online Server Preview in your on-premises environment if you don’t already have it.
MAPI over HTTP is the default for Outlook connectionsIn Exchange 2016, MAPI over HTTP is enabled by default, and offers additional controls, such as the ability to enable or disable MAPI over HTTP per user, and whether to publish it to external clients.
Exchange 2013 Architecture:
|Image Source: Microsoft|
Exchange 2016 Architecture:
|Image Source: Microsoft|
As you can see in above figures, Microsoft has introduced architectural change in exchange 2016. Below is the list of what is missing in Exchange 2016 in comparison with Exchange 2013.
Client Access server role
- Client Access Service replaces client access server role.
- This service runs on the Mailbox server role.
- The Mailbox server role now performs all functionality that was previously included with the Client Access server role.
- The MAPI/CDO library has been replaced by Exchange Web Services (EWS), Exchange ActiveSync (EAS), and Representational State Transfer (REST)* APIs.
- If an application uses the MAPI/CDO library, it needs to move to EWS, EAS, or the REST APIs to communicate with Exchange 2016.
De-emphasized features in Exchange 2016
The following features are being de-emphasized in Exchange 2016 and may not be included in future versions of Exchange.
- Third-party replication APIs
- RPC over HTTP
- Database Availability Group support for failover cluster administrative access points
Read more about Exchange 2016 architecture in Part I: Exchange 2016 architecture.