Exchange 2016 CU5 Released

Exchange 2016 CU5 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 CU5

This is build 15.01.0845.034 of Exchange 2016 and the update is helpfully named ExchangeServer2016-x64-CU5.iso which allows us to easily identify the update.  Details for the release are contained in KB 4012106.

Note that CU6 will have changes and improvement to TLS, specifically TLS 1.2.

Updates Of Particular Note

CU5 contains the latest time zone updates

As announced in the Exchange CU4 release post the .NET framework requirement has changed.  Exchange 2016 CU5 requires .NET framework 4.6.2.  Since .NET 4.62 framework support was first added in CU4, this adds an upgrade item.  Ideally Exchange 2016 servers will already be on that CU4 build and .NET can be upgraded prior to installing CU5.  If not, upgrade to CU4, do the .NET upgrade and then upgrade to CU5.

Issues Resolved

KB 4015665 SyncDelivery logging folders and files are created in wrong location in Exchange Server 2016

KB 4015664 A category name that has different case-sensitivity than an existing name is not created in Exchange Server 2016

KB 4015663 "The message content has become corrupted" exception when email contains a UUE-encoded attachment in Exchange Server 2016

KB 4015662 Deleted inline picture is displayed as attachment after you switch the message to plain text in Exchange Server 2016

KB 4015213 Email is still sent to Inbox when the sender is deleted from the Trusted Contacts list in Exchange Server 2016

KB 4013606 Search fails on Exchange Server 2016 or Exchange Server 2013

KB 4012994 PostalAddressIndex element isn't returning the correct value in Exchange Server 2016

Issues Not Resolved

CU5 has some issues which could not be addressed prior to release.

  • When attempting to enable Birthday Calendars in Outlook for the Web, an error occurs and Birthday Calendars are not enabled.
  • When failing over a public folder mailbox to a different server, public folder hierarchy replication may stop until the Microsoft Exchange Service Host is recycled on the new target server.

Fixes for both issues are planned for CU6.


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…

  • 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 maintenance mode prior to installing, confirm the install then take the server out of maintenance mode
  • Restart the server after installing the CU
  • 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.
  • 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!
  • CU5 does not contain new AD Schema updates for your organisation, though depending upon which version of Exchange you are upgrading from, changes may be required.


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.




Comments (34)
  1. Exadmin says:

    tried to upgrade Exchange 2016 CU 2 to CU5 in Lab, it prompts with .net 4.62, applied, restarted. upgraded the first server with no issues. the second servers gave me hard time. I used the cmd line to do unattended installation, the first time hung at removing Exchange files… just closed cmd windows, restarted the upgrade, this time hung at Mailbox role – frontend transport role 58%… more than 12 hours. What should I do the next… TIA

    1. Hayden says:

      Upgrade to cu4 first. Install .net 4.6.2, then install cu5.

    2. Hayden is correct. You should have moved to CU4, updated .NET then you can install CU5. That process is outlined above, and fleshed out a bit more in this post:

      If I’m understanding the above correctly, you now have an unsupported version of .NET on that box with Exchange 2016 CU2. You will need to back that down to a supported version. This post should help with that

      If you need more assistance, I would get a support case open ASAP.


  2. Marcus Petersson says:

    One issue with CU5 is that you can’t have swedish character replacements in the address policies, which we’ve had since the mid 90’s. For us the setup crashed without notice at 95% on the Mailbox Role – Mailbox Service, nothing about the problem in the ExchangeSetup.log, the logging just cuts off. I had a case with Microsoft and the support engineer had got two other cases with the exact same issue with CU5, both coming from Sweden as well. To be able to upgrade we had to temporarily remove the swedish character replacements.

    1. Hi Marcus – I was indeed monitoring those discussions.

      One question I did have is around the format of your EAP. What were all of the addresses that the EAP was generating? Looked like quite along list.
      Use as an example, don’t write your real domain.


      1. Joachim Sehlsted says:

        We have the same problem with address polices after upgrading from CU4 to CU5. The upgrade went fine, but after that we were unable to edit users where the following policy would apply:

        Changing it to:

        solved the problem for now.

        With the first policy the app pool would crash:
        A process serving application pool ‘MSExchangeECPAppPool’ suffered a fatal communication error with the Windows Process Activation Service. The process id was ‘24488’. The data field contains the error number.

      2. Marcus Petersson says:

        Our EAP’s looked like this:

        Recipients: Resource mailboxes
        Recipients filter: ((RecipientType -eq ‘UserMailbox’) -and (ResourceMetaData -like ‘ResourceType:*’) -and (ResourceSearchProperties -ne $null))

        Default Policy
        Recipients: All recipient types
        Recipients filter: Alias -ne $null

        1. Fred Proos says:


          We have Estonian characters in our EAP’s : %räa%rüu%rõo%röo%rÄA%rÜU%rÖO%rÕO%g.%räa%rüu%rõo%röo%rÄA%rÜU%rÖO%rÕ
          Are these characters supported in CU5 or i should postpone my installation til its fixed.

          1. Most likely this will be the same thing Fred. Note that I have not tested it, but suspect that will be the case………


  3. Jesper says:

    Hi, and Office 365 has the ability to share calendars inside your organization. If you accept those invitations in OWA they will be accessible in your iPhone via ActiveSync. Is this feature coming to Exchange 2016?

    1. Adam S says:

      Thank you for this information. Much appreciated.

  4. MSchueler says:

    After the successful update I have the following problem:

    I would like to use, as so often before today, the CMDLET “Set-Mailbox” (, to change mailbox alias. I also use this CMDLET by PowerShell Script to provisioning user with mailbox.

    After Update 2x Exchange 2016 Nodes from CU3 to CU5 (include DotNet 4.6.2. update before) I receive the following error only for users with special characters (like Müller, Peter), not sure why?

    My Test are:
    1. I tried with Exchange Management Shell direct from Exchange Servers 2016 CU5 himself or typical with PSSession against the 2x ExNodes from diffrent clients.
    2. With other Set-Mailbox Identity Parameter (SamAccountName, DN, Alias, GUID, SMTP Address)
    3. The issue only appears by user objects with special characters üöä etc. attributes.

    The error occurs for example by:

    1. Set-Mailbox -Identity “GUID” -Alias “NewAlias” -WhatIf

    or same without Parameter “WhatIF” or by

    2. Set-Mailbox -Identity “GUID” –HiddenFromAddressListsEnabled $True -WhatIf


    The address ‘SMTP:M.Mÿller@domain.tld’ is invalid: Specified argument was out of the range of valid values.
    Parameter name: The address ‘M.Mÿller@domain.tld’ is not a valid SMTP address.
    + CategoryInfo : NotSpecified: (:) [Set-Mailbox], DataValidationException
    + FullyQualifiedErrorId : [Server=ExNode,RequestId=7d559cda-6ea3-4b8e-b467-94daca3b170e,TimeStamp=4/13/2017 10:
    53:03 AM] [FailureCategory=Cmdlet-DataValidationException] ABCF52BB,Microsoft.Exchange.Management.RecipientTasks.S
    + PSComputerName : ExNode.domain.tld

    Get-Mailbox -Identity “GUID” | select PrimarySmtpAddress, Guid, Alias, Database
    shows the current active information and address:

    PrimarySmtpAddress Guid Alias Database
    —————— —- —– ——–
    M.Mueller@domain.tld d967a947-6263-45e1-8c5b-8c833581d4ca alias EXDB

    Has anyone noticed this? Maybe a DotNet issue?

    1. Yes – this is an issue.

      Can you please open up a support case so that we can track this, and ensure that we have the right visibility.


      1. MSchueler says:

        Hi Rhoderick,
        we are normal end customers without direct Microsoft Support. Can I still open a case and if so, where?


      2. MSchueler says:

        Hi Rhoderick,

        another question and need your knowledge again.

        Unfortunately, I have seen your article ( ) later as my update time from CU3 to CU5, where it was pointed out first to install CU4, not as expected directly to CU5 …

        Very annoying and I’m now worried about the state of my Exchange Servers Nodes because with the present knowledge and the information posted on the download link website here, I have not installed CU4 first … Not good or? … damned 🙁
        “It’s not necessary to install any Exchange Server 2016 cumulative updates or service packs that were released before Cumulative Update 5 before you install this update.”

        Whatever else, except the described error with CMDLET Set-Mailbox, the environment seems to work normally.
        Both ExchangeSetup Log Files shows at last: “The Exchange Server setup operation completed successfully.”
        (Update procedure was >> ExNode Start Maintenance >> Install Dot.Net 4.6.2 >> Reboot >> Windows Update >> Reboot >> CU5 >> Reboot >> ExNode Stop Maintenance)

        My questions are therefore:

        1. How can I check if the installation is valid and stable or support now?
        2. If no, what can I do so that both nodes can run properly as CU5? A downgrade is not possible, as far as I know?
        3. A downgrade to CU4 is not possible, as far as I know?

        I would be glad about an answer and change accordingly the note on the download page or better still fit for further CU setup’s routine to check the CU4 is present!


        1. Hi Manfred,

          The issue with EAP and Set-Mailbox should not be related to your upgrade order. If the setup logs completed OK, and you then immediately went to CU5 then you should be in a good position.

          You are correct – there is no uninstall routine for CU5 to CU4. Or from CU5 to CU3. That would mean building a new CU3/4 server and moving mailboxes to it.


  5. Stijn Teijssen says:

    Thanks for the write-up, good stuff! After upgrading our server to CU5 I can no longer move mailboxes from Exchange 2010 to 2016 which worked well before. The status is “StalledDueToSourceMailboxLocked”. Is this a known issue or should I contact MS support (somehow)?

    1. Stijn Teijssen says:

      Extra information: moving mailboxes to a CU4 servers works fine, moving those over to the CU5 server doesn’t. After clicking to complete the move it seems to restart the entire move. Bad item limit is set to 100 in both cases to be sure.

      1. Stijn Teijssen says:

        Solution found, apparently I didn’t enter all processes to exclude in our antivirus, which turned out to be the culprit!

        1. Andreas says:

          I have exactly the same problem. Which exclusions did you add?

          1. Review all of them.

            And pay attention to different config options around the on-access vs on-demand tasks. Also Mount Points……

            Call the AV vendor on a conference call with all stakeholders – I have always found them great to work with. The issue is normally the on-site AV people…..


  6. Andrew says:

    if you use backup exec or veeam, you will no longer be able to restore individual mailboxes or mail items at this stage

    1. Adam S says:

      Thanks for mentioning this Andrew.
      It’s much appreciated.

  7. Will Fulmer says:

    Any other information on this issue? Anyone with a case open with Microsoft able to get any insight as to if this bug/issue is acknowledged and if they are planning a CU5v2 release or will this be fixed in CU6?

    This is also relevant to anyone levering Knoll OnTrack PowerControls for Exchange – whether white-labelled with NetApp as Single Mailbox Recovery (SMBR) or Rubrik – Item Level Recovery

  8. ExAdmin2 says:

    Has anyone attempted to install Exchange Server 2016 *CU5* on Windows Server 2016? No matter what I try, I cannot get it to work. If I install Exchange Server 2016 CU5 on a brand new Windows Server 2016, I make it all the way to the prereq checker and fail atthe server-gui-mgmt-infra error that we used to see prior to CU3 and CU4. But if I try installing CU4 first, and then upgrade to CU5, I get the “missing .NET framework 4.6.2” error from the moment I double click on the setup.exe file (i.e. it fails even earlier in the process). I have confirmed that .NET framework 4.6.2 is installed as part of the Windows Server 2016 cumulative update, so I know that’s not the actual issue — especially since I only got that error after installing CU4 (i.e. without CU4 on that Windows Server, I made it past the 4.6.2 check and got all the way to the pre-req checker in the install wizard).

    1. Zoltan Gomori says:


      I installed CU5 on clean, full pached Windows Server 2016 without problem. I had problems, when I tried to remove it because of the problems mentioned above.


  9. Mason says:

    Per the CU5 update download page:

    It states:

    “The Cumulative Update 5 package can be used to run a new installation of Exchange Server 2016 or to upgrade an existing Exchange Server 2016 installation to Cumulative Update 5.

    It’s not necessary to install any Exchange Server 2016 cumulative updates or service packs that were released before Cumulative Update 5 before you install this update.”

    Your write-up says to go from RTM to CU4 to CU5, but the above seems to contradict this?

    1. Yes the CU5 package can do both an upgrade and a fresh install.

      Though you must also factor in .NET support requirements.

      WRT the upgrade scenario – the change .NET support was previously announced and Ideally would have been updated and prepped to streamline this change. If not, then it will add more work at this point in time.


  10. kenn Chukwu says:

    I completed the upgrade from CU3 to CU5 on two distinct networks. Upon completion, Client Side Rules created on Outlook 2010/2016 stopped working. Have since then relied on creating rules from the ECP. Users’ really need to have that ability to create their own rules.

  11. Victor Lambert says:

    Another CU installed (CU5), another issue with Lagged Copies…
    After installing CU5 (2 weeks ago), all 14day Lagged Copies are either ReplayQueue of 0 or Unhealthy with ReplayQueue of 10Ks
    I removed one 14day LaggedCopy, deleted the dir files and recreated with 14day Lag and Pref4, wait for reseed…ReplayQueue back to 0
    Any ideas?? We got burned on CU4 with LaggedCopies going into AutoSuspend (undocumented feature of CU4)


  12. David-Mac says:

    I have multiple Exchange 2016 servers behind a hardware load balancer. I updated one of the server to CU5 (did the CU4 first) and every since then random users are getting repeated password prompts in Outlook 2010, 2013 and 2016. I disabled the CU5 updated server from the load balancer and the problem seems to go away. Anyone else seem any issues with repeated password prompts in CU4 or CU5?

    1. David-Mac says:

      I have multiple Exchange 2016 servers behind a hardware load balancer. I updated one of the server to CU5 (did the CU4 first) and every since then random users are getting repeated password prompts in Outlook 2010, 2013 and 2016. I disabled the CU5 updated server from the load balancer and the problem seems to go away. Anyone else seem any issues with repeated password prompts in CU4 or CU5?

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