Exchange 2016 Architecture

Exchange Server 2016 mainly refers to single building block architecture which offers email services for implement at all sizes, from small enterprises to the giant multi-national corporations. This architecture is depicts via following diagram.


Exchange 2016- Architecture

Individual components are illustrates via following sections.

1.    Server communication architecture
2.    Server role architecture
3.    High availability architecture
4.    Client access protocol architecture
5.    Exchange 2016 architecture changes

1) Server communication architecture

Communication performed among Exchange 2016 servers and past and future upcoming versions of Exchange generally occur at the protocol layer. Cross-layer communication is not permitted. Such communication architecture can be denoted as “every server is an island”. This architecture has the following benefits:


  • Reduced inter-server communications.
  • Isolated failures.
  • Integrated design inside each server.
  • Version-aware communications.

Protocol layer communication among Exchange 2016 servers is displayed below via diagram.

Exchange 2016 Mailbox Server


2) Server role architecture

Mailbox servers and Edge Transport servers is used by Exchange 2016. These server functional roles are elaborated in the following sections.


Mailbox servers


  • Mailbox servers consist of the transport services which are used to route mail.
  • Mailbox servers consist of the mailbox databases which process, render, and store data.
  • Mailbox servers consist of the client access services which accept client connections for all protocols. These frontend services are core responsible for routing or proxying connections to the respectively corresponding backend services on a Mailbox server. Clients does not connect directly to the backend services.
  • Mailbox servers consist of the Unified Messaging (UM) services which provide voice mail and other telephony functional features to mailboxes.
  • You manage Mailbox servers by utilizing the Exchange admin center (EAC) and the Exchange Management Shell.

Edge Transport server’s functional role

  • Edge Transport servers control and manage all external mail flow for the Exchange enterprises and organization.
  • Edge Transport servers are generally installed in the perimeter network, and are followed subscription to the internal Exchange organization. The EdgeSync synchronization process develops recipient and other configuration information present to the Edge Transport server as mail enters and evacuates the Exchange organization.
  • Edge Transport servers provides antispam and mail flow guidelines, rules and regulations as mail enters and leaves to evacuates your Exchange organization.
  • You control, manage and handle Edge Transport servers by using the Exchange Management Shell.

3) High availability architecture

The high availability functional properties in Exchange 2016 are described in the given sections below:

The Property of Mailbox high availability

A database availability group (DAG) is the basic underlying element of the high availability and site resilience framework that’s developed into Exchange 2016. A DAG is a category of Mailbox servers which host a set breed of databases and offers automatic, database-level recovery from database, server, and network failures. And DAGs in Exchange 2016 have been enhanced in comparison to Exchange 2013.
The Property of Transport high availability

  • The Transport service builds redundant clone copies of every message in transit. This functional feature is also known as shadow redundancy.
  • The transport service builds redundant clone copies of every delivered message. This functional feature is also known as Safety Net.
  • In Exchange 2016, a DAG depicts as a transport high available boundary. You can attain site resilience by spanning a DAG over multiple Active Directory sites.
  • In Exchange 2016, transport high capability is much more than a best effort for message redundancy, as redundancy doesn’t bank upon on supported functions & features of the sending mail server. Hence, Exchange 2016 strives to guarantee message redundancy by keeping intact multiple copies of messages during and after delivery.


4) Client access control protocol architecture

The control of client access services on Exchange 2016 Mailbox servers is accountable for accepting all kinds of client connections. The client access (frontend) services proxy all these connections with the backend services on the destination Mailbox server (the local server or a remote Mailbox server which holds the active replication of the user’s mailbox). Clients do not directly connect or communicate to the backend services. Such communication is depicted in the following diagram.

Exchange 2016 Mailbox Server with client access

The protocol which is used by a client regulates and controls the protocol that’s used to proxy the request to the backend services on the destination Mailbox server. For instance, the client communicating and connected using HTTP, the Mailbox server uses HTTP to proxy the request for the destination Mailbox server (secured via SSL utilizing a self-signed certificate). In case the client used IMAP or POP, then the protocol which is used is IMAP or POP.

Telephony requests are variant than other client connections. Rather than of proxying the request, the Mailbox server redirects the prompting request to the Mailbox server which holds the active copy of the user’s mailbox. Telephony devices are needed to establish their SIP and RTP sessions directly with the Unified Messaging services on the destination Mailbox server.

5) Exchange 2016 architecture changes

•    Server role consolidation- In earlier versions of Exchange, you are allowed to install the Client Access server role and the Mailbox server role/functions on separate computers. In Exchange 2016, the Client Access server function and role is automatically installed and setup as part of the Mailbox server functional role, and the Client Access server functional role is not available as a segregated installation option. Such alteration reflects the philosophy of Exchange server functional role co-location which is been recommended best practice since Exchange 2010. A multi-role Exchange server architecture provides the tangible benefits mentioned below:


a) All Exchange servers as per your environment (with the most likely exception of any Edge Transport servers) can be perfectly the same—the same configuration, the same hardware, etc. Such uniformity simplifies and ease the hardware purchasing, also maintenance and management of the Exchange servers.
b) You may most likely require fewer physical Exchange servers. Resulting in lower ongoing maintenance costs, very few Exchange server licenses, and minimized rack, floor space, and power needs.
c) Extensibility, Scalability is improvised, as you’re distributing the workload over a greater number of physical machines. At the time of a failure, the load on the remaining left Exchange multi-role servers maximizes only incrementally, that ensures the other functions on the Exchange servers aren’t adversely affected.
d) Resiliency is enhanced, as a multi-role Exchange server can survive with a much greater number of Client Access role (or service) failures and still continue to provide service.


•    Search enhancements – The local search instance is now capable to read data from the local mailbox database replica or a copy. Consequently, passive search instances no longer require coordinating with their active counterparts to conduct index updates, and bandwidth needs between the active copy and a passive replica have been minimized by 40% in comparison to previous versions of Exchange. Also, search is now able to conduct multiple asynchronous disk reads prior to a user finishing a search term. Such act populates the cache with relevant information, and offers sub-second search query latency for online clients like Outlook over the web.


•   Office Online Server Preview for Outlook over the web document preview– In the earlier versions of Exchange, Outlook Web App consists of WebReady Document Viewing for the default built-in preview of Office and PDF documents. In Exchange 2016, Outlook on the web utilizes Office Online Server Preview to offer rich preview and editing/amending abilities for documents. When this offers a consistent document experience with other products like SharePoint and Skype for Business, it do need you to deploy and implement Office Online Server Preview in your on-premises environment in case you don’t already have it.


•    MAPI over HTTP is the default for Outlook connections-  MAPI over HTTP was briefed and introduced in Exchange 2013 Service Pack 1, and provides improvements over the conventional Outlook Anywhere (RPC over HTTP) connection method. In Exchange 2016, MAPI over HTTP is capably enabled by default, and provides additional controls, like the ability to enable or disable MAPI over HTTP per user, and whether to advertise it to external clients.

Kristin is a content strategist at Techarex Networks. Kristin follows the B2B technology space closely and loves to write on the latest changes in technology, futuretech and fixes for day to day how to issues. Besides writing Kristin also loves music, moves and skating.

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