Outlook 2016: What Exchange admins need to know
Published Nov 19 2015 06:00 AM 176K Views

At the end of September, we released Office 2016, which includes a new version of the Outlook desktop client. Hopefully you’ve seen already seen some of what’s new in Outlook 2016 for end users – if not, here’s a quick overview. Today we want to take a closer look at some changes in Outlook 2016 that matter to Exchange administrators, to help you plan your organization’s deployment:

MAPI-HTTP and Autodiscover

As with all Outlook releases, this one comes with several updates to improve performance and reduce the common issues users face connecting to their accounts and syncing mail. We’ve reduced the amount of time it takes to download messages, display the message list, and show new email after resuming from hibernation. Over the past two releases, we’ve also made significant changes to how Outlook connects to and sync mail from Exchange, including:

  • Outlook 2016 requires AutoDiscover. AutoDiscover must be configured or Outlook 2016 will be unable to connect to Exchange Server. Outlook 2016 retrieves Exchange connectivity settings directly from AutoDiscover instead of the registry, making profiles more reliable, but that also makes AutoDiscover a required feature. If you have not yet configured AutoDiscover, you will need to do this prior to deploying Outlook 2016. More information can be found here: Account Auto Configuration process (Autodiscover).
  • New MAPI-HTTP protocol. First introduced in Exchange 2013 SP1 and Outlook 2013 SP1, MAPI-HTTP has replaced the RPC-based sync with a new Internet-friendly protocol that enhances Exchange/Outlook connectivity. You can read more about this architecture change and what it means for you by checking out this EHLO blog from last year.
  • Foreground network calls eliminated. Outlook no longer uses foreground network calls to ensure that Outlook stays responsive on unreliable networks.

Outlook 2016 will not connect to Exchange Server 2007

Outlook 2016 does not connect to Exchange 2007, as Outlook 2016 requires technology (e.g. sync, search, auto-discover) present in Exchange 2010+. As an Exchange 2007 customer, it will be important to keep this in mind as you plan your upgrade cycles for both Exchange Server and the Office clients, to make sure you don’t get stuck in a bad place.

In order to prevent any issues for customers using the Office 2013 apps in Office 365 ProPlus with Exchange 2007, we temporarily disabled auto-updates for users currently connected to Exchange 2007. The Office 2013 apps in Office 365 ProPlus will continue to be supported with updates until September 2016, by which customers will need to update their Exchange Server. More details about temporarily staying on and receiving updates for Office 2013 can be found here: Prepare to update Office 365 ProPlus to the Office 2016 version.

New Sync Slider options

Outlook 2013 saw the introduction of the Sync Slider, which helps limit the size of OST’s by controlling how much recent mail was synced locally on the device. For Exchange accounts, this was 12 months by default, with options to go down to ‘1 month’ or up to ‘all mail’. In 2016, we’ve added more sync options that allow for better storage management by only retaining 3, 7, or 14 days of mail on the device. You can also adjust this using Group Policy.

New search behavior

We’ve improved the reliability and performance of Outlook search by integrating the server-side search engine in Exchange 2016 and Office 365 (Exchange Online) and leveraging this search as the default Outlook search index. By default, Outlook will search the entire mailbox and return search results beyond what is just synced down in the OST file. This means less user frustration when they cannot find older emails, and no more having to use the “Click here to view more on Microsoft Exchange” option to find mail on the server. Search just works like a user would expect it to, without any additional configuration steps by users or admins in either Outlook 2016 or Exchange 2016.

Of course, this Exchange-based search requires an internet connection. Offline searches will continue to leverage the Windows search index, which has also been updated with better error handling and retry logic and increased search result cap (from 30 to 250).

People pane off by default as Outlook social connector is no longer active

The People pane is off by default in Outlook 2016. Previously, the People Pane showed information from your personal social networks here via the Outlook social connector. Some 3rd party services made changes to their APIs that resulted in their social activity being no longer available. While it will still provide views into Mail, Attachments and Calendar events from the people involved in your email, we made the decision to turn this off by default and put the focus on providing more room for the reading pane.

The People pane can be re-enabled by users by going to View > People Pane > Normal.

Certain Outlook 2016 features require specific Exchange Server versions or Office 365

Some new Outlook 2016 features requires certain version of Exchange Server or Office 365. The primary features that have requirements are:

  • The Exchange-based search discussed above requires the underlying technology be available in Exchange 2016 or Office 365.
  • Cloud based attachments require Exchange 2016, SharePoint 2016 and Office Online Server 2016 (the latter two of which are currently in preview) or Office 365.
  • Clutter and access to Office 365 Groups requires connections to Exchange Online mailboxes.

For more detail, see Outlook 2016 feature support by Exchange Server version.

New authentication options (for Office 365 customers only)

Outlook moves from Basic to Active Directory Authentication Library (ADAL)-based Authentication, also known as Modern Authentication, for Office 365 (Exchange Online) mailboxes.

Modern Authentication provides Outlook 2016 with several benefits:

  • Single sign-on (SSO). Outlook now support single sign in with other Office applications.
  • Multi-factor authentication. Outlook will support multi-factor authentication (MFA). MFA secures the user sign-in beyond just a single password. When enabled, users are required to acknowledge a phone call, text message, or app notification on their smartphones after correctly entering their passwords. Sign in is only confirmed after this second authentication factor has been satisfied.
  • No more basic auth: Prior to Modern Authentication, Outlook would connect to Exchange Online using Basic auth over HTTPS. This required the username and password to be provided anytime a connection to Exchange Online is made. Modern Auth flows negate the need for this type of basic authentication. Instead, the Outlook client now communicates directly with the customer’s Identity Provider and no longer needs to share the user’s password with Exchange Online for user authentication.

You can more read about Modern Authentication here an d here.


That concludes our tour of what’s changed in Outlook 2016, from an admin perspective. We hope this overview will be useful as you prepare for your organizations deployment. Let us know if you have any additional questions in the comments, and be sure to check out the Office 2016 Deployment Guidance on TechNet to learn even more about implementing Office 2016 in your organization.

The Exchange Team

1 Comment
Version history
Last update:
‎Jul 01 2019 04:25 PM
Updated by: