**Microsoft** has issued a firm reminder to its customers: security updates for **Exchange Server 2016** and **2019** under the Extended Security Update (ESU) program will cease in October 2026. This decision marks a definitive end to support, with no further extensions planned. The initial ESU program began in October 2025, following the end of mainstream support for **Exchange Server 2016** in October 2020 and **Exchange Server 2019** in January 2024. A six-month extension to the ESU program was announced in April 2026, creating a “Period 2” for updates. ### End of the Line for Exchange ESU Despite the previous extension, the **Exchange Server** team recently clarified the situation in a blog post: "Over the last several weeks we have received several questions about possible extension of the **Exchange Server 2016/2019** ESU program past October 2026... There will be no further extension of **Exchange 2016/2019** ESU program timeline. Once October 2026 ends, there will be no further updates for **Exchange 2016/2019**, even if you currently have a Period 2 ESU." This unequivocal statement leaves no room for doubt regarding the October 2026 deadline. ### Urgent Call to Upgrade or Migrate In light of this, **Microsoft** is strongly advising IT administrators to take immediate action. The recommended path for **Exchange Server 2019** users is to upgrade to **Exchange Server Subscription Edition (SE)**. This process is designed to be an in-place upgrade, similar to applying a Cumulative Update (CU). For organizations still operating **Exchange 2016** or even **Exchange 2013** in production environments, the guidance is to either upgrade directly to **Exchange Server SE** or first migrate to **Exchange 2019** as an intermediate step. Comprehensive migration guidance for **Microsoft 365** is available on **Microsoft's** official documentation site. This resource offers detailed steps for global administrators looking to transition to **Exchange Online**, which can be deployed as a standalone service or as part of an **Office 365** subscription. ### Broader Support Context This announcement for **Exchange Server** comes amidst other recent **Microsoft** support updates. In June, the company quietly extended the free **Windows 10** ESU program for consumers by an additional year, pushing its end-of-support to October 2027. More recently, **Microsoft** also noted that **Windows Server 2022** and **Windows 11 24H2 Home** and **Pro editions** will reach their end of mainstream support in 90 days but will continue to receive security updates under extended support.