Exchange Server 2016 and the End of Mainstream Support
Published Aug 10 2020 07:59 AM 75.3K Views

UPDATE 2/12/21

The Exchange Sustained Engineering Team continued servicing all customer issues for Exchange 2016 that were opened with Microsoft by the end of Mainstream Support, which was Oct 13, 2020. Some of these cases were being worked on by customers and Microsoft into the new year, with fixes being approved though the end of January. As such, not all fixes will be in the soon-to-be-shipped March update (CU20), as code stabilization and quality targets do not allow us to take changes that late in the shipping cycle. Therefore, we have decided to extend out one more CU and we will be shipping CU21 in June 2021. New cases are not being considered for CU21; this is only to complete our commitment to fix what was approved from the cases that were logged prior to the end of Mainstream Support. Microsoft encourages Exchange Server 2016 customers to adopt CU21 as soon as possible after it’s released in June, 2021 to ensure uninterrupted delivery of any future security related fixes. After June 15, 2021, only CU21 or its successors will receive updates. During the Extended Support phase, only the latest CU is eligible to receive updates once the standard 3 month transition period of the prior CU has lapsed.


As hopefully many of you already know Exchange Server 2016 enters the Extended Support phase of its product lifecycle on October 14th 2020. That’s just a few short months away.

During Extended Support, products receive only updates defined as by the Fixed Life Cycle. For Exchange Server 2016, Fixed Life Cycle will include any required product updates due to security and time zone definition changes. With the transition of Exchange Server 2016 to Extended Support, the quarterly release schedule of cumulative updates (CU) will end. The last planned CU for Exchange Server 2016, CU20, will be released in March 2021. This is a change from earlier blog notes because it became clear that CU19 in December 2020, was too close the end of Mainstream Support to process all of the cases that came in by Oct 13th.   

There is one more consideration for this change that we want to address here today, and that is the ongoing use of Exchange Server 2016 for recipient management for hybrid organizations that have moved all their mailboxes to the cloud.

As you probably also know we have historically provided a free license for these ‘management’ servers if their only use is to properly manage Exchange attributes when recipient objects are mastered on-premises. You also know that we never provided this free license type for Exchange Server 2019.

We want to assure you that we are still committed to delivering a solution that will allow these lingering servers to be removed, but it will not arrive before Exchange Server 2016 enters Extended Support.

For this reason, we want to make our recommendation for this scenario clear. Our broad recommendation is to keep Exchange Server 2016 in production use until such point as we release a solution that allows those servers to be removed. As explained earlier, Extended Support still provides security and time zone updates and so keeping them in production and ensuring they are properly patched does not increase your risk profile in any way.

If you can’t move your mailboxes to the cloud and you plan on keeping mailboxes on-premises, then you really should be moving to Exchange Server 2019, and using that for both mailboxes and hybrid connectivity. That way you get full support including non-critical bug fixes and get ongoing product improvements.

When we have a solution available to allow any management-only servers to be removed, it may require an update to Exchange Server 2016, and in that case we may release a future CU or patch. Currently there is no plan to release future updates for Exchange 2016, but we want to assure our customers that if we need to do this to support the removal of these ‘management only’ servers, we will.  

Microsoft encourages Exchange Server 2016 customers to adopt CU20 as soon as possible to ensure uninterrupted delivery of any future security related fixes. After March 16, 2021, only CU20 or its successors will receive updates. During the Extended Support phase, only the latest CU is eligible to receive updates once the standard 3 month transition period of the prior CU has lapsed.  

Updates will continue to be made available via Windows Update and the Microsoft Download Center. Additional lifecycle information for all Microsoft products is available on

We hope this update was informative and we look forward to hearing your feedback and answering any questions you may still have.

The Exchange Team

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‎Feb 12 2021 07:22 AM
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