Microsoft has certainly embraced the quarterly update cadence for Exchange server! This month the Exchange Server team is releasing updates for all currently supported versions of Exchange:

Here’s a few of the key points from the Microsoft Exchange Team blog:

  • All of the updates include an update to the OWA S/MIME control to sign the control with a SHA-2 compliant certificate. S/MIME users will need to reinstall the control to receive the update.
  • Exchange 2016 updates are now shipping as ISO files instead of self-extracting EXEs. I have no idea who was asking Microsoft to make that change, but it surely wasn’t anyone here in Australia who now needs to download a 3x size file over our terrible internet connections.
  • Exchange 2013 CU12 reverts the mailbox anchoring that was introduced in CU11 and caused some unexpected issues. It’s good to see Microsoft responding to the issue by rolling this back (for now).
  • Exchange 2010 gets support for the new standalone Hybrid Configuration Wizard.

Some additional notes:

  • Exchange 2016 CU1 includes schema changes
  • Exchange 2013 CU12 does not include schema changes from CU11, but may include RBAC changes, and may involve a schema update if you’re upgrading from a build prior to CU11. It’s generally recommended to run /PrepareAD anyway, or upgrade your first server with Enterprise Admins and Schema Admins so that the AD prep can automatically run for you.
  • .NET 4.6.1 remains unsupported on Exchange servers for now
  • If you’re running Exchange on Windows Server 2012 R2, review this known issue that causes Exchange updates to install very slowly.

Deploying Updates

Exchange Server 2016:

Exchange Server 2013:

Exchange Server 2010:

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. George Jones

    【He brought my Ex Lover back Contact Robinsonbuckler11 @ gmail com】……

  2. Chris

    I have just updated Exchange 2013 SP1 with cumulative 12, after the server reboot outlook clients can longer get email. Webmail ISO are woring fine. IIS still have back end and front end directories.
    Any ideas on what I should try to fix it?

  3. David_TAI

    Hybrid environment with 2 Exchange 2013 servers–Multi Role and Office 365.
    The last update I did was from CU3 to CU7. First server went without a hitch. Second server–not so much. It failed due to the issue of 2 connectors being configured as Hub Transports. Got them switched over to Frontend Transports and the CU7 update installed fine. Getting ready to go from CU7 to CU12. I have 2 connectors that are still configured as Hub Transports–even after the CU7 update. One is labeled as a Client Proxy and the other is labeled as Default . The same goes for the second Exchange Server–same 2 connectors. I did not do the original configuration these servers so I’m not sure if those are default connectors of custom connectors.
    Can those be left alone or do I need to reconfigure them as Frontend Transports before I upgrade to CU12? If I do reconfigure them as Frontend Transports, will that affect mail flow?

  4. Mateusz

    I’m preparing to install Exchange Server 2016 in an Office 365 deployed environment. We currently don’t have any on-premises Exchange servers deployed and we have some about 100 users mailboxes hosted in Exchange Online. Are there any issues that could occur after deploying a on-premises Exchange server?

  5. Kevin Robinson

    Exchange 2016 CU1 breaks the search in Outlook 2016 operating in cache mode, search is capped at 25 items when the scope is set to Current Folder or Current Mailbox .

  6. Michel Zehnder

    Is there any indication if they will support WMF5 for Exchange 2013 at some point?

  7. David Bogar

    6.1 GB Is a huge update! Everything good with my latest update.

  8. Antonio Francisco Vanucchi

    I don´t have much time to research this, so, I uninstalled update roll-up 13, then I applied update roll-up 12 and in sequence I applied update roll-up 13 and everything is fine. Thanks for your return, bye

  9. Antonio Francisco Vanucchi

    First: Sorry my poor English. I still have a little customers using Exchange 2010 SP3. I installed all updates rollups in this servers since that they was released with no problems, until now. Recently, I made a new fresh install of Exchange 2010 in new server, I applied the service pack 3 and for last I applied update rollup 13. Now, the windows update offers me to install the update rollup 12 and I don´t know why. Assuming that update rollup 13 contains all fixes of its predecessors, why windows update still offers me the update rollup 12. This is a bug of the install process??? Thank You for any help.

    1. Avatar photo
      Paul Cunningham

      My system is not doing the same thing, so I’m unable to reproduce your problem scenario. It may be a Windows Update issue, or it may be something specific to your server.

  10. Patrick

    Hi there,

    we’are planning to update from Exchange 2013 CU11 to Exchange 2016 soon. As we installed CU11 for Exchange 2013, we ran the AD Schema upgrade process. Today as in preparation for Exchange 2016 we ran the AD Schema upgrade process for it too. Is there any need for a prepareAD and could there be any problems by running Exchange 2013 in a co-existence with Exchange 2016?

    1. Avatar photo
      Paul Cunningham

      Yes you will need to do the AD prep for Exchange 2016.

      There are no co-existence bugs between Exchange 2013 and 2016 that I’m aware of. The products are designed to work together in co-existence, provided that you follow the configuration guidance.

  11. Michael

    I had a look the other day for E2016 CU1 and it’s 6.1GB!!! I’m guessing that includes all other languages.

    But 6.1GB!!! Bigger than the RTM. That is crazy.

    1. Avatar photo
      Paul Cunningham

      The larger size is because of the change to .ISO format for distributing the updates.

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