Microsoft officially ended support for Exchange Server 2019 on October 14, 2025. That includes not just mainstream support, but all security updates and patches. If you’re still running on-premises Exchange—even in a hybrid environment—this change demands your attention.
In this article, I’ll break down a few options for moving forward, highlight some licensing complexities, and share insights based on my own experience helping organizations through this transition.
Microsoft offers Exchange Server SE (Subscription Edition) as the successor to Exchange 2019.
Let’s break down the “Subscription” requirements for Exchange SE and the important considerations.
Clarifying your licensing model early is essential to avoid unexpected costs or compliance gaps. See Microsoft's FAQs around this topic on their website here.
You need to know what version you're running and what cumulative update level you're on before you can plan your next move. If your organization is already running Exchange 2019 CU15, you're in a good position: upgrading can be a relatively straightforward in-place process. For anyone behind that mark, the process becomes significantly more complex. If you're on Exchange 2013, for instance, you'll need to:
The more outdated your environment, the more steps and risk you incur. Version inventory is your essential first step. Kudos to the Exchange team for the great documentation on this topic. Here is a link to the Microsoft Exchange Team’s article, which gives a full table of Exchange Versions and the steps required to update like the example above.
You might be surprised to learn you can now decommission your last on-premises Exchange Server, even if your organization still uses Active Directory and hosts all mailboxes in Microsoft 365.
Most of the customers I work with who are still running Exchange on-premise are doing so solely for user and recipient management. That typically includes tasks like modifying aliases, converting mailboxes, or updating distribution lists. But in Exchange 2019 CU12, Microsoft introduced the Exchange Management Tools, which let you perform those same functions without needing to keep a full server online. You can install the tools on a central management server—or even a technician’s workstation, provided the proper permissions are in place.
This is a meaningful change for organizations that want to fully retire Exchange infrastructure but still rely on AD-based recipient management. Read more on this topic from Microsoft here.
If your organization needs a little more time to finalize its migration, Microsoft now offers a 6-month Extended Security Update (ESU) program for Exchange Server 2016 and 2019. This program provides Critical and Important security updates beyond the official end-of-support date of October 14, 2025, and is valid through April 14, 2026.
Key points:
This option is best suited for organizations:
To enroll, contact your Microsoft account team starting August 1, 2025 for pricing and details.
Important: Microsoft has stated clearly that this ESU period will not be extended past April 2026, so it should be viewed as a short-term safety net—not a long-term strategy.
Even if your Exchange 2019 environment appears to be stable, it is now officially unsupported.
Some organizations don’t fully realize the risk. If any part of your Exchange footprint is exposed to the internet and no longer receiving security updates, you're operating with a significant vulnerability. In an era of ransomware and zero-day exploits, running unsupported mail infrastructure is not just an inconvenience—it’s a security liability.
Whether you plan to upgrade to Exchange SE or eliminate on-prem Exchange altogether, the key is planning. Start with:
At Prescriptive, we can help with all of this. From assessment to implementation, our team has deep experience guiding organizations safely through the Exchange evolution.