Microsoft has reminded that Exchange Server 2016 and 2019 reached the end of support and advised IT administrators to upgrade servers to Exchange Server SE or migrate to Exchange Online.
According to Redmond's product lifecycle website, Exchange 2016's mainstream support ended in October 2020, while Exchange 2019 reached the mainstream support end date in January 2024.
The company has also reminded customers in January and September that Exchange Server 2016 and 2019 will reach the end of support this month.
After the October 2025 Exchange Server Security Updates, Microsoft will stop issuing time zone updates and security patches to address vulnerabilities that may expose servers to breaches.
It will also cease providing technical support, including bug fixes for newly discovered issues that may impact the stability and usability of outdated servers.
"Today, October 14, 2025, Exchange Server 2016 and Exchange Server 2019 reach end of support. It's critical to upgrade now to remain supported and secure," the Exchange Team said in a Tuesday blog post.
"Customer installations of Exchange 2016 and Exchange 2019 will continue to run after October 14, 2025. However, continuing to use these offerings after the end-of-support date invites potential security risks, so we strongly recommend taking action now."
Upgrade or migrate
Microsoft advised admins to migrate to Exchange Online (available as a standalone service or as an Office 365 subscription) or upgrade to Exchange Server Subscription Edition (SE).
As the company explained, they can perform in-place upgrades from Exchange Server 2019 to Exchange Server SE, a process identical to installing a Cumulative Update (CU).
Admins who still have servers running Exchange 2016 or 2013 are advised to upgrade to Exchange Server SE or, first, install Exchange 2019.
You can find detailed Microsoft 365 migration guidance for global admins on Microsoft's documentation site, which can also help decide the best Exchange Online migration path.
"We strongly believe that customers get the best value and user experience by migrating fully to Exchange Online or Microsoft 365. Migrating to the cloud is the best and simplest option to help you retire your Exchange Server deployment," Microsoft added today.
"When you migrate to the Microsoft cloud, you make a straightforward hop away from an on-premises deployment and benefit from new features and technologies, including advanced generative AI technologies that are available in the cloud but not on-premises."
Microsoft has also reminded customers that Windows 10 reached the end of support today and will no longer release patches for newly discovered Windows 10 security vulnerabilities.