Update 7/15/2025: Added a mention of Exchange 2016/2019 ESU program.
In May 2024, we shared our Exchange Server Roadmap Update and our plans for the future of Exchange Server. Since then, we’ve bee...
Updated Aug 13, 2025
Version 17.0
Blog Post
I believe this Decommissioning Exchange Server 2016 - Microsoft Community Hub this, Upgrading your organization from current versions to Exchange Server SE - Microsoft Community Hub (this Article) and elsewhere indicate that no, Exchange 2016 (or 2019) cannot co-exist with Exchange SE CU1.
- "Setup in Exchange Server SE CU1 will block coexistence with all unsupported versions (e.g., Exchange Server 2013, Exchange Server 2016, Exchange Server 2019) and allow coexistence only with Exchange Server SE."
While it appears you can install Exchange SE RTM with Exchange 2016, Exchange SE RTM is more a transitional build preparing folks for the "meat" of SE which will begin with SE CU1.
Additionally, Exchange 2016 will be End-Of-Life October, 2025, and once unsupported, would start to be vulnerable to unpatched bugs, security issues, etc...
"With the release of Exchange Server SE CU1, Exchange Server SE will be the only supported version, and it will remain that way."