16/09/2026
Exchange Server 2016 and 2019 reached end of support on 14 October 2025. Free security updates stopped that day.
Since then, the only patches have come through Microsoft's paid Extended Security Update program. That programme closes next month, and there is no further extension.
I upgraded three on-prem Exchange 2019 servers to Subscription Edition last week. One standalone, two DAG members.
From CU15, the move to SE is an in-place upgrade. It installs much like a normal cumulative update. Same server, same hardware, no mailbox migration. My own server took about 35 minutes.
What made it smooth was preparation, not luck.
I ran Microsoft's Health Checker script first and cleared what it flagged: page file size, outdated Visual C++ runtimes, a power plan still set to Balanced, .NET strong crypto settings. Then a fresh backup, a snapshot, antivirus paused, databases and queues checked. For the DAG I moved the databases to the other node and worked through one server at a time.
The part worth knowing: after the upgrade, Windows Update works again.
On Exchange 2019 it had gone quiet. Every update released after 14 October 2025 goes through ESU, and nothing on the server tells you. Patching simply stops, and months pass before anyone notices.
ESU closes in October 2026. If this is on your list for later, later is now about four weeks away.
The upgrade is smaller than the procrastination.
https://edywerder.ch/exchange-server-health-check-powershell/
Exchange Server Health Check with PowerShell: run Microsoft's Health Checker script, work through 11 manual checks, and see what out-of-support really means.
