Throttling and Blocking Email from Persistently Vulnerable Exchange Servers to Exchange Online

Kenneth650
That will all be covered here in this post or ones like it:

Exchange Server Roadmap Update - Microsoft Community Hub

Changes to support Exchange Server Subscription Edition

• Removal of support for co-existence with Exchange 2013. Since Exchange 2013 reached end of life last year, and since Exchange Server SE does not support coexistence with any unsupported versions, in preparation for what comes next, we are removing support for Exchange Server 2013. Customers should remove Exchange 2013 servers before installing Exchange 2019 CU15 or Exchange Server SE RTM or later. If Exchange 2013 is detected in the environment, Setup in CU15 and Exchange Server SE will stop and display an error message to this effect.
• Support for new product keys. New product keys will need to be obtained for other server roles, except for Hybrid servers which will continue to receive a free license and product key via the Hybrid Configuration Wizard. CU15 adds support for these new keys, which will be available when Exchange Server SE is available.
• Support for Windows Server 2025. Today, Exchange 2019 can be installed on Windows Server 2019 and Windows Server 2022. CU15 will introduce support for Windows Server 2025 (when the OS reaches GA later this year).