Microsoft Exchange 2016 & 2019 ESU Program Comes to an End This October

Microsoft dropped a pretty important notice this week: the Extended Security Updates (ESU) program that many enterprises have relied on for Exchange Server 2016 and Exchange Server 2019 is winding down. The final round of patches will be pushed out on October 15, 2024, and after that the code‑base will go dark – no more official security fixes, no more bug‑splats from the Redmond team.

Why does this matter? Well, ESU is the safety net that lets companies keep an older Exchange version running past its mainstream‑support deadline without throwing their entire mail infrastructure into chaos. It’s a paid add‑on, meant to buy you time while you sort out a migration to newer on‑premises gear (like Exchange 2022) or to Microsoft 365. With the program ending, that window is closing fast.

To put the timeline in perspective, Exchange 2016 entered mainstream support back in 2015, moved to extended support in 2022, and now, thanks to ESU, got a few extra months of peace of mind. Exchange 2019, which is still in its mainstream‑support phase, likewise benefitted from the same ESU extension. Once the October deadline passes, any vulnerabilities discovered will stay unpatched unless you’re running a supported version.

The message from Microsoft is crystal clear: start planning now. Whether that means upgrading to the brand‑new Exchange 2022, shifting mailboxes to Exchange Online, or even consolidating workloads onto Azure, the sooner you act, the smoother the transition will be. IT teams are already scrambling to inventory their Exchange footprints, check licensing, and map out migration pathways.

For those still on older Windows Server platforms (think Server 2012 R2), remember that those OS versions are also hitting end‑of‑support around the same time. It’s a perfect storm of expiration dates, and ignoring it could leave your organization exposed to security risks – something no CIO wants to admit in a boardroom.

In short, the October 15 deadline is a hard stop. No more updates, no more loopholes, just a clear signal to move forward. If you haven’t already opened a ticket with your Microsoft account team, now’s the time.