The end of support for Exchange Server 2019 and 2016 is approaching. Support for both versions will end on October 14, 2025, from which date only Exchange Server SE (Subscription Edition) will be supported. However, upgrading to Exchange SE is much easier this time than before, at least if Exchange Server 2019 is already in use. Here is a brief overview of the options.
Upgrade from Exchange Server 2019 to Exchange Server SE
If Exchange Server 2019 is already in use, the upgrade to Exchange Server SE is comparatively simple: Only one update needs to be installed on the Exchange 2019 servers. The update to Exchange Server SE is therefore installed directly on the Exchange 2019 servers, just like a CU. This is therefore an in-place upgrade; a migration in which Exchange Server SE is installed on new servers is not necessary in this case.
To ensure that the upgrade to Exchange SE can be installed smoothly, Exchange Server 2019 CU15 should be installed first. The CU15 is expected in 2024, so it should be released soon. The CU15 will also be the last CU for Exchange 2019, after that there will only be security updates until 14.10.2025 if this becomes necessary. The CU15 cannot be installed if Exchange 2013 servers are still in use. Exchange 2013 servers must be updated before installing the CU15 be migrated. The CU15 also blocks the installation of Exchange 2013 servers. The inplace upgrade of Exchange 2019 servers will also be possible with the CU14, which is already is available. So if Exchange 2019 is used, the upgrade to Exchange SE will be a simple matter. Exchange Server SE is expected in the second half of 2025.
However, a migration from Exchange 2019 to Exchange Server SE is required if the operating system is to be updated. If Exchange SE is to run on Windows Server 2025, a conventional migration is required again, as the inplace upgrade of the operating system is not yet supported.
Exchange Server SE RTM (the first published version) will not bring any functional changes compared to CU15. In principle, only the name and the type of licensing will change, nothing more. New features will only come with CU1 for Exchange SE. CU1 is expected at the end of 2025. The CU1 for Exchange Server SE will then end the coexistence for Exchange 2019 and Exchange 2016, so all previous Exchange versions must be replaced before the CU1 is installed.
Upgrade from Exchange Server 2016 to Exchange Server SE
If Exchange Server 2016 is still in use, it is not possible to upgrade directly to Exchange Server SE. In this case, the classic Migration to Exchange Server 2019 then the inplace upgrade to Exchange SE can be carried out. If anyone is still using Exchange 2016, I would wait a little longer before migrating to Exchange 2019. Windows Server 2025 is about to be released, so before installing Exchange 219 on Windows Server 2022, you can also wait a little longer until the CU15 for Exchange 2019 is released and Windows Server 2025 is also available. Exchange SE will then run directly on Windows Server 2025 and not on Windows Server 2022. As already mentioned, no inplace upgrade of the operating system is supported. Here is another nice graphic:
Exchange Server SE and licensing
Licensing for Exchange Server SE is the same as for Exchange Server 2019, with one exception: Microsoft no longer only offers the purchase of licenses. Previously, you could buy an Exchange Server 2019 license and CALs separately, but this is no longer possible.
For Exchange Server SE, in addition to purchasing the required server licenses and CALs, customers must also maintain an active subscription. This means that they must either purchase the following:
Microsoft 365 Cloud license for all users and devices that access Exchange SE (e.g. Microsoft 365 E3 or E5 licenses) or Exchange Server SE server licenses and CALs with Software Assurance (SA). So if you are already running Exchange Server with SA, you can simply keep and renew your SA and use Exchange Server SE. So nothing changes here. Anyone who does not have Software Assurance (SA) for Exchange Server can now either take out an SA or purchase Microsoft 365 licenses for all users who access Exchange Server SE. In principle, this means that even small companies can still use Exchange Server SE if no cloud is required.
As now, Exchange SE continues to offer free licenses for hybrid use via the Hybrid Configuration Wizard (HCW). In contrast to previous versions, however, either an SA or Microsoft 365 licenses (E3 / E5) must be purchased for this license in order to receive Exchange Server updates. So it is not completely free, but at least you save the Exchange Server license.
Exchange Server SE hardware requirements
The same hardware requirements apply for Exchange SE as for Exchange Server 2019, only the name and licensing changes with the RTM for Exchange SE. The code remains the same, so there are no other hardware or other requirements. So 128GB RAM is still required ;-)