For some reason I’ve seen a bunch of forums posts and emails about new Exchange Server 2013 deployments in the last week. The timing is notable, because Exchange Server 2013 has entered the “extended support” phase of its support lifecycle as of April 10th (a few days ago).

From Microsoft’s announcement:

With the transition of Exchange Server 2013 to Extended Support, the quarterly release schedule of cumulative updates will end. The last planned cumulative update for Exchange Server 2013, Cumulative Update 21, will be released in June 2018. Microsoft may at its discretion release a future cumulative update to aggregate previously released critical updates or to address unforeseen future O365 Hybrid connectivity requirements. At this time there is no explicit plan to exercise releasing future cumulative updates.

So… that’s the end of Exchange 2013 feature development. It hasn’t received significant new features in a long time anyway, but the transition to extended support pretty much seals the deal. If you’re on Exchange 2013 today, make sure you update to CU21 when it is released in June so that you can continue to receive security updates during the extended support phase.

If you are planning a new Exchange on-premises deployment today, you should deploy Exchange Server 2016. The exception would be if you are still, for some reason, running Exchange Server 2007 in your environment. In that situation, an Exchange 2013 migration must be used as an intermediate step to Exchange 2016, because Exchange 2007 and 2016 can’t co-exist in the same organization.

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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. Michael Russo

    I wish CU21 was the last one and they would just put security updates on top. Now I have to spend hours installing CU23 on various servers just to get the latest security update (sigh).

  2. Martinss


    I have tried to install the CU21 in our Exchange 2013 (Two servers in DAG), but we had two problems. The first problem was about the installation of .net 4.7.1,( where we tried twice without success. After search a little, I found this link ( After use this new package, it was possible to install the .NET version. .

    The second problem is about our UM. When we were in the upgrade process, we received an error message about the requisite to uninstall the pt-BR from UM to be possible to run the CU21. It was not possible to uninstall the pt-BR plugin in that moment, because we have a lot of users who use this feature, and we had not plan this new task. .

    Some questions:

    Have you already have the experience to uninstall the UM package, install the CU21 and after that install again the UM package?

    Did you have any user impact executing this procedure?

    Do you have any tip about this scenario?

    Thank you in advance.


  3. Stiliyan Stoychev

    When created a DPL rule witch scan for ‘SWIFT Code ‘ or ‘IP Address ‘ or ‘International Banking Account Number (IBAN) ‘ or ‘EU Debit Card Number ‘

    And Do the following…
    Set audit severity level to ‘Medium’
    and Send the incident report to mailbox ************@*********.com, include these message properties in the report: sender, recipients, subject, cc’d recipients, bcc’d recipients, severity, sender override information, matching rules, false positive reports, detected data classifications, matching content, original mail.

    All seems to be okay but i want to send incident reports to mail enabled public folder and here is the problem.
    I cannot select the mail witch is responsible to deliver message in this folder.
    Check and folder is not hidden from address book , i check also who have permission to view or edit this folder too and all ok.

    Its possible in Ex2013CU21 to this or only way is to send to real mailbox or resource mailbox.
    Any help will be welcome.

  4. MarcK4096

    Another reason for a new Exchange 2013 deployment is if you haven’t rid the environment of Outlook 2007. Office upgrades can be quite expensive in large organizations.

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      Paul Cunningham

      Sure, but deploying an extended maintenance server because of an EOL desktop client is just compounding the problem.

      1. MarcK4096

        I would argue Exchange 2013 on newer hardware is better than Exchange 2010 on older hardware. The purist in me agrees with you. But, if use of Outlook 2007 is something outside of your control, then upgrading to Exchange 2016 is simply off the table. The remaining choice is to stay with the aging deployment or move to Exchange 2013.

  5. Gaza

    I am planning to deploy an Hybrid Exchange 2013 and Office 365 am I obliged to update the server to the latest CU ? I would prefer not having to update the server…

    ALso i hear there is something like putting the server in the maintenance mode before applying the CU . if I lunch the CU does the server Goes automatically to the maintenance Mode?

    1. Avatar photo
      Paul Cunningham

      Yes, you are required to keep your hybrid servers up to date with supported CUs.

      Maintenance mode mostly applies to servers responsible for hosting mailboxes and mail flow. If your server only exists for the hybrid management purposes, you could skip those steps if you want to (the CU setup process does do some stuff to put the server into maintenance mode, just not everything). But if you want to take the lowest risk approach, you will just follow the documented update process every time.

  6. 2007Q

    is Exchange 2007 and 2013 on premises can coexist in a hybrid with 365 while all the MB on prem are on 2013 and some of MB migrated to 365 (which is on Exchange 2016) ? (2007 should stay for legal reasons to be able to restore old MB if needed)

    1. Avatar photo
      Paul Cunningham

      Yes, but Exchange 2007 is unsupported, so keeping it alive in your environment is a potential security risk, could impact the stability of your environment, and will also be a deployment blocker when you try to install Exchange 2016 or any later version of Exchange.

      I recommend you come up with a restore solution that doesn’t involve keeping the Exchange 2007 server running. Several backup vendors have tools for extracting data directly from the database file without needing a server running.

  7. Hayden

    Looking forward to a new migration guide when CU21 comes out

  8. Doug

    What are the smtp relay options in 365?

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