End of the ESU program for Exchange Server 2016/2019

Maxime Hiez
Exchange
24 Aug, 2026

Introduction

On August 14, 2026, the Exchange Server team put an end to the speculation : the Extended Security Update (ESU) program for Exchange Server 2016 and Exchange Server 2019 does stop in October 2026, with no further extension. After that date, no update will be released for these two versions anymore, including for the organizations enrolled in period 2 of the program.

Check the article about the end of support for Exchange Server 2016 and 2019 HERE.

What the ESU program allowed

Mainstream support for Exchange Server 2016 and 2019 ended on October 14, 2025. The ESU program acted as a paid safety net for the organizations that had not completed their migration by that date, by continuing to deliver security updates only, for a limited period.

That safety net disappears in October 2026. The servers will keep working, but any vulnerability discovered after that date will remain without a fix, including critical vulnerabilities that can be exploited remotely. This is the point to escalate to the management teams that keep postponing the topic.

The two possible paths

Microsoft keeps the same two options :

Migrate to Microsoft Exchange Online

The most direct path to leave the server update cycle for good, with native integration to the Microsoft 365 services.

Upgrade to Exchange Server Subscription Edition (SE)

The option to stay on-premises, under a subscription model :

From Exchange 2019 CU14 or CU15, the in-place upgrade to Exchange SE RTM is possible and Microsoft presents it as a low risk operation. The SE RTM version is indeed code identical to Exchange 2019 CU15, apart from the license terms, the product name and the build number.
From Exchange 2016, the in-place upgrade isn’t supported. You have to go through a legacy upgrade, with new servers in coexistence then mailbox moves, towards Exchange 2019 CU15 or directly towards Exchange SE RTM.

On the licensing side, Exchange 2019 and Exchange SE have the same requirements, which limits the budget impact of the edition change to the subscription itself.

A point of attention on the schedule

The release of Exchange SE CU1 has been delayed, Microsoft having prioritized the AI-assisted vulnerability research work on the product. This shift changes nothing to the October 2026 deadline, but it deserves to be integrated in a migration plan that would target a specific cumulative update. Planning on Exchange SE RTM remains the safe path.

Conclusion

Microsoft’s answer is unambiguous : there will be no new extension. The organizations still running Exchange 2016 or 2019 in production have two months to settle their path and start the work. Between Exchange Online and Exchange SE, the choice depends on the hosting strategy, but standing still is no longer a tenable option after October 2026.