Microsoft has released new updates for all supported versions of Exchange Server, announcing:

The Exchange 2010 and 2007 updates contain daylight saving time fixes, as both of those versions of Exchange are in extended support now.

A public folder indexing issue experienced by some customers who upgraded to Exchange 2013 CU14 or Exchange 2016 CU3 last quarter are now fixed in these latest releases for those two versions of Exchange. Microsoft’s advice is:

To ensure all public folders are indexed appropriately, all public folder mailboxes should be moved to a new database after applying the appropriate cumulative update released today.

When Exchange 2016 CU3 was released, it became the first version of Exchange to support installation on Windows Server 2016. Shortly after that release it was discovered that there was a bug with Exchange 2016 DAG members running on Windows Server 2016 that would result in repeated crashes of IIS on the server. The Windows Server team has released an update that fixes the underlying issue, and all Exchange 2016 deployments on Windows Server 2016 require that update to be installed.

Both Exchange 2013 and 2016 now also support .NET 4.6.2, and Microsoft encourages you to deploy .NET 4.6.2 as soon as possible, because it will be the required version for Exchange 2013/2016 releases from March 2017 onwards.

For user-facing changes, Exchange 2016 CU4 also includes an update to the Outlook on the web (OWA) UI to align with the latest experience in Exchange Online, with a new compose interface that moves a bunch of stuff around and forces us to retrain our muscle memory 😉

Exchange 2016 CU4 OWA UI modeled by Brent Alinger, Microsoft Principal Program Manager


About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for


  1. Amit

    I am having trouble installing CU4. Below is what the prereq analysis returns…of course none of that is actually true…

    C:\Windows\system32>u:\Setup.EXE /prepareschema /IAcceptExchangeServerLicenseTerms

    Welcome to Microsoft Exchange Server 2016 Cumulative Update 4 Unattended Setup

    Copying Files…
    File copy complete. Setup will now collect additional information needed for installation.

    Performing Microsoft Exchange Server Prerequisite Check

    Prerequisite Analysis 100%

    Setup can’t contact the primary DNS server ( using TCP port 53. Check that the IP address of the DNS server is correct and
    that the DNS server is reachable.
    For more information, visit:

    The Active Directory schema isn’t up-to-date, and this user account isn’t a member of the ‘Schema Admins’ and/or ‘Enterprise Admins’
    For more information, visit:

    Setup encountered a problem while validating the state of Active Directory: Exchange organization-level objects have not been created, and
    setup cannot create them because the local computer is not in the same domain and site as the schema master. Run setup with the /prepareAD
    parameter on a computer in the domain and site , and wait for replication to complete. See the Exchange setup log for more information
    on this error.
    For more information, visit:

    The forest functional level of the current Active Directory forest is not Windows Server 2003 native or later. To install Exchange Server
    2016, the forest functional level must be at least Windows Server 2003 native.
    For more information, visit:

    Either Active Directory doesn’t exist, or it can’t be contacted.
    For more information, visit:

    The Exchange Server setup operation didn’t complete. More details can be found in ExchangeSetup.log located in the
    :\ExchangeSetupLogs folder.


    1. Avatar photo
      Paul Cunningham

      You should log a support case with Microsoft. If it’s a bug they’ll need to see cases of it so that they can fix it.

  2. Jason Trimble

    The URLs to download the updates do not appear to work anymore.

  3. John Bales

    “To ensure all public folders are indexed appropriately, all public folder mailboxes should be moved to a new database after applying the appropriate cumulative update released today.”

    So, if we have CU13 and move directly to CU15, do we still have the task of moving the public folders to another database after the upgrade?

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