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Surprise changes in the Exchange 2016 release

Exchange 2016 brought mixed feelings for admins who felt like the release was more of an Exchange 2013 Service Pack than a new version. See which changes made it to the final release.

Microsoft rolled out the on-premises successor to Exchange Server 2013: named Exchange Server 2016. The release came with some much anticipated changes -- mostly stemming from developments in Exchange Online as part of Office 365 -- and some pleasant and unpleasant surprises.

After word from Microsoft Ignite 2015 and with the release of the Exchange 2016 preview, the major version number of Exchange 2016 remained unchanged; like its predecessor, the build number for Exchange 2016 is 15 -- its predecessor remained 15. This almost immediately made people treat the Exchange 2016 release as a service pack, rather than a whole new product. Quickly, the Exchange 2016 release became more or less known as Exchange 2013 Service Pack 2. For this same reason, IT organizations about to migrate to Exchange 2013 may decide to skip Exchange 2013, and go straight to Exchange 2016.

Keeping the major version number identical also created some issues. For example, some scripts look at the major version number only to determine against what Exchange version they are running.

Worse, the Exchange team also made a small mishap: You can create database availability groups (DAGS) with mixed Exchange 2013 and Exchange 2016 member servers, and these DAGs are unsupported. This could also potentially corrupt databases due to differences in the internal database structure. Until Microsoft solves this in an update of Exchange 2013 as well as Exchange 2016, prevent this situation with strict operational procedures or technically with cmdlet extension agents.

Exchange 2016 preferred changes

One major advantage of the Exchange 2016 release, which originates from what Microsoft called the "every server is an island" principle, is that it offers a flexible upgrade path from Exchange 2013. You can opt for a down-level or up-level migration scenario, which means Exchange 2016 can proxy traffic to Exchange 2013, and vice versa. It allows you to deploy a mix of Exchange 2016 and Exchange 2013 servers, even from the load balancer level. This eliminates the need to upgrade Internet-facing servers first.

Another major architectural change is the emphasis of multirole server deployment by removing the option to deploy the client access server of Mailbox Server roles individually. This has become the preferred architecture since Exchange 2010, so this change in the Exchange 2016 release enforcing multirole deployments shouldn't come as a surprise.

The preferred architecture for Exchange 2016 now also recommends Resilient File System for storing Exchange databases and log files, which was still optional with Exchange 2013.

What didn't make it?

A feature that unexpectedly didn't make Exchange 2016 RTM was search indexing from passive database copies. This would be a considerable bandwidth saver compared to when mailbox servers copy indexes from the mailbox server with the active copy instead of creating the index from the passive copy they already host. This feature will likely be introduced in a future Cumulative Update.

Another feature available in preview but not the Exchange 2016 release is auto-expanding Archive, which scales archived mailboxes as they expand. Auto-expanding Archive is available in Exchange Online.

New features in Outlook on the Web are direct ports from Exchange Online, like the ability to sweep, pin and undo. In combination with the Office Online Server 2016 product, formerly known as Office Web Apps Server, the Exchange 2016 release allows Outlook on the Web users to view and edit supported attachments side-by-side, where Exchange will leverage the Office Online Server to render the attachments. Office Online Server 2016 is currently in preview.

Another feature stemming from Office 365 is Modern Attachments, which allows users to send attachments by storing them on OneDrive for Business. The email contains a link to the attachment, and the sender can provide information such as if the recipient is allowed to edit the attachment. This requires SharePoint 2016, which is also currently still in preview.

Modern Attachments in Office 365
Send attachments with OneDrive for Business in Office 365

A minor change in the Exchange 2016 release is that MAPI/HTTP will be the default protocol for Outlook clients to connect. MAPI/HTTP requires Outlook 2013 SP1 or later; older clients will resort to traditional Outlook Anywhere (RPC/HTTP) connections. The goal of MAPI/HTTP is to deliver a better end-user experience at the start of Outlook and while working over unreliable Wi-Fi connections.

With the Exchange 2016 release, some things are also deprecated. For example, Outlook 2007 is no longer supported, nor is coexistence with Exchange Server 2007. Third-party software using the MAPI/CDO libraries to interface with Exchange will also stop working.

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