Exchange 2016 CU6 Released

Exchange 2016 CU6 has been released to the Microsoft download centre!  Exchange 2016 has a different servicing strategy than Exchange 2007/2010 and utilises Cumulative Updates (CUs) rather than the Rollup Updates (RU/UR) which were used previously.    CUs are a complete installation of Exchange 2016 and can be used to install a fresh server or to update a previously installed one. Exchange 2013 has the same servicing methodology.

Download Exchange 2016 CU6

This is build 15.01.1034.026 of Exchange 2016 and the update is helpfully named ExchangeServer2016-x64-CU6.iso which allows us to easily identify the update.  Details for the release are contained in KB 4012108.

.NET Framework 4.7 is not supported at the time of writing.

No Exchange 2010 updates were released today since Exchange 2010 is in extended support.  Updates will be released as per the extended support lifecycle policy.

Exchange 2007 is no longer supported, updates are not provided once a product has exited out of extended support.

Updates Of Particular Note

CU6 contains the latest time zone updates

There  is now improved support for TLS 1.2.  TLS 1.0 and 1.1 should not be disabled at this time.

As announced in the Exchange 2016 CU5 release post the .NET framework requirement has changed.  Exchange 2016 CU5 onwards require .NET framework 4.6.2.  Please see Exchange 2013 CU16 and Exchange 2016 CU5 .NET Framework Requirement for more details.

Two major features were added to Exchange 2016 with the CU6 release: Sent Items Behaviour Control and Original Folder Item Recovery.  The latter is a feature which has been requested for many, many years.  Admins, rejoice!!

Issues Resolved

KB4024658 FIX: The EAS web.config file is not updated on the CAFE server during a build-to-build upgrade

KB4024654 POP/IMAP clients can't log on with NTLM when Alias and SamAccountName are different in Exchange Server 2016

KB4024653 Active Monitoring probes fail when you use a new accepted domain as the default domain in Exchange Server 2016

KB4024652 Repeated IMAP SEARCH BODY requests may not return newly delivered messages in Exchange Server

KB4024651 The "MessageRetrievalMimeFormat" setting isn't honored for plain text-only email messages in IMAP in Exchange Server

KB4024650 Emoji is displayed as question marks in iOS clients in an Exchange Server environment

KB4024649 The Read or Unread flag isn't synchronized correctly after you turn off an ActiveSync device overnight in Exchange Server

KB4024648 FIX: A new contact created in OWA may be merged into an existing contact on Exchange Server 2016

Some Items For Consideration

Exchange 2016 follows the same servicing paradigm for Exchange 2013 which was previously discussed on the blog.  The CU package can be used to perform a new installation, or to upgrade an existing Exchange Server 2016 installation to this CU.  Cumulative Updates are well, cumulative.  What else can I say…

For customers with a hybrid Exchange deployment, must keep their on-premises Exchange servers updated to the latest update or the one immediately prior ( N or N-1).

  • Test the CU in a lab which is representative of your environment
  • Review this post to also factor in AD preparation which is to be done ahead of installing the CU onto the first Exchange server
  • Follow your organisation’s change management process, and factor the approval time into your change request
  • Provide appropriate notifications as per your process.  This may be to IT teams, or to end users.
  • After you install this cumulative update package, you cannot uninstall the cumulative update package to revert to an earlier version of Exchange 2016. If you uninstall this cumulative update package, Exchange 2016 is removed from the server.
  • Place the server into SCOM maintenance mode prior to installing, confirm the install then take the server out of maintenance mode
  • Place the server into Exchange maintenance mode prior to installing, confirm the install then take the server out of maintenance mode
  • I personally like to restart prior to installing CU.  This helps identifies if an issue was due to the CU or happened in this prior restart, and also completes any pending file rename operations.  3rd party AV products are often guilty of this
  • Restart the server after installing the CU
  • Ensure that all the relevant services are running
  • Ensure that event logs are clean, with no errors
  • Ensure that you consult with all 3rd party vendors which exist as part of your messaging environment.  This includes archive, backup, mobility and management services.
  • Ensure that you do not forget to install this update on management servers, jump servers/workstations and application servers where the management tools were installed for an application.  FIM and 3rd party user provisioning solutions are examples of the latter.
  • Ensure that the Windows PowerShell Script Execution Policy is set to “Unrestricted” on the server being upgraded or installed.  See KB981474.
  • Disable file system antivirus prior to installing. Do this through the appropriate console.  Typically this will be a central admin console, not the local machine.
  • Verify file system antivirus is actually disabled
  • Once server has been restarted, re-enable file system antivirus.
  • Note that customised configuration files are overwritten on installation.  Make sure you have any changes fully documented!
  • CU6 does contain new AD Schema updates for your organisation.

Please enjoy the update responsibly!

What do I mean by that?  Well, you need to ensure that you are fully informed about the caveats with the CU  and are aware of all of the changes that it will make within your environment.  Additionally you will need to test the CU your lab which is representative of your production environment.



Rhoderick Milne [MSFT]

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