Microsoft: Exchange 2016 reaches extended end of support in October

​Microsoft reminded today that Exchange 2016 will reach the end of extended support next year on October 14 and shared guidance for admins who need to decommission outdated servers.

Exchange 2016 reached its mainstream end date in October 2020, while Exchange Server 2013 (the previous version) reached its extended end-of-support (EOS) date on April 11, 2023.

"If you plan to stay on-premises, we recommend moving to Exchange 2019 as soon as possible. Only Exchange 2019 will support in-place upgrades to Exchange SE, marking the first time in many years that you can perform an in-place upgrade on any Exchange release," the Exchange team warned.

"You should start decommissioning Exchange 2016 servers in favor of Exchange 2019 now, to be ready for easy in-place upgrades to Exchange SE when it becomes available."

The company recommends putting Exchange 2016 servers into maintenance mode for one week after migrating to a newer version of Exchange Server to identify any unforeseen issues.

Admins are advised to ensure that all such issues are resolved before uninstalling Exchange 2016. Microsoft also warned that shutting down the servers without a proper migration plan may cause problems unless done within a scheduled change control window.

Enabling maintenance mode before uninstalling Exchange 2016 allows admins to confirm there are no connections to the servers. If there are any, they need to be identified and updated to use the new Exchange servers.

"Even after reviewing messaging and connectivity logs, it's not uncommon for an organization to keep their legacy Exchange servers online (in Maintenance Mode) for a period long enough to find issues with unknown processes, unexpected recovery efforts, etc," the Exchange team added.

"To put an Exchange server into maintenance mode, see the Performing maintenance on DAG members section of Manage database availability groups in Exchange Server. For additional information on Exchange Server component states, see this blog post."

In January, Microsoft also announced the end of mainstream support for the Exchange Server 2019 on-premises mail server software, which will also reach its end of extended support on October 14, 2025.

Admins are advised to switch to Exchange 2019 to keep receiving security updates—CU15 (H2 2024) in the second half of 2024—or migrate to Microsoft's hosted Exchange Online (available as a stand-alone service or an Office 365 subscription).

Redmond's documentation site provides Microsoft 365 migration information and detailed guidance for global admins to help decide the Exchange Online migration path.