Last Minute Lifeline
Microsoft will officially end support for Exchange Server 2016 and Exchange Server 2019 on October 14, 2025. This deadline has been known for a while. However, for organizations that might not complete their migrations on time, Microsoft has offered a last-minute “security lifeline”: the Extended Security Update (ESU) program.
What Does It Mean?
In short, this program allows Exchange 2016 and 2019 servers to receive critical and important security updates for an additional six months (until April 14, 2026). These updates won’t be publicly available; they will only be provided to customers who purchase ESU. An important point: this is not a support extension. The products will still be out-of-support, and you won’t be able to open general support cases. Only updates released under ESU will be supported. Furthermore, Microsoft does not guarantee monthly updates—if no critical issues are identified, no updates will be issued during this period.
Who Is It For?
• Organizations still running Exchange 2016 CU23 or Exchange 2019 CU14/CU15,
• Companies that have started migrating to Exchange Subscription Edition (SE) but need a bit more time,
• Large IT environments unable to complete the migration by October 2025.
Program seems reasonable “insurance policy” for organizations racing against the clock. But Microsoft’s message is clear: do not treat this as a long-term strategy. ESU is only a short-term security buffer.
In the long run, everyone needs to move to Exchange Subscription Edition (SE). Microsoft has transitioned to a modern lifecycle policy, retiring the old extended support models. So this 6-month ESU is basically the last remnant of the old approach.
Bottom Line
If your IT environment is still running Exchange 2016/2019, you have two options:
- Complete the migration to Exchange SE as soon as possible.
- If that’s not feasible, contact your Microsoft account team to purchase an ESU license.
Remember: April 14, 2026 is the absolute cutoff. After this date, there is no further extension.