Upgrading your organization from current versions to Exchange Server SE

In May 2024, we shared our Exchange Server Roadmap Update and our plans for the future of Exchange Server. Since then, we’ve been asked some questions whose answers we think you’ll find helpful.

First, here are some terms used in this post:

• CU stands for Cumulative Update
• SU stands for Security Update
• CY stands for Calendar Year
• H1 / H2 stand for First half / Second half (e.g., of a CY)
• RTM stands for Release to Manufacturing (refers to the first release of a software product)
• Coexistence refers to versions that can exist in the same Exchange organization

The upgrade path from Exchange Server 2016 and Exchange Server 2019 to Exchange Server Subscription Edition (SE) is different from what we’ve done in the past for several reasons, so we want to first provide details on various scenarios, timelines, and actions to take, and then we have an FAQ at the end of this post with some helpful answers.

All Exchange Server customers are affected by these changes, whether fully on-premises, in a hybrid state, or in a management tools only state (for recipient management).

What are we releasing, and when?

In our roadmap post, we detailed the next three releases for Exchange Server:

1. Exchange Server 2019 CU15
2. Exchange Server SE RTM
3. Exchange Server SE CU1

Here is a table summarizing these releases and their implications on coexistence with previous versions:

Support status of Exchange Server versions

The last three versions of Exchange Server, their lifecycles, and how they are affected by the above releases are detailed in the following table:

All other versions and builds of Exchange Server are unsupported, except for Exchange 2019 CU13, which will go out of support when Exchange 2019 CU15 is released.

Coexistence of different versions in the same organization

We’re making changes in Exchange Server that affect coexistence with older versions in the same organization. In the past, it was possible for you to continue running an older (and even unsupported) version of Exchange Server in an organization that had newer version(s) of Exchange Server. This is changing in two very important ways:

• Setup in Exchange Server 2019 CU15 and Exchange Server SE RTM will block coexistence with Exchange Server 2013.
• 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.

When Exchange Server SE CU1 is released, all other versions of Exchange Server will be out of support. As detailed in the following table, to install CU1 (or later) you will have to first decommission and remove all older versions of Exchange Server from your organization.

Getting from a mixed version organization to an Exchange Server SE organization

To get from where you are today to Exchange Server SE only, you have some options.  At this point, you should be running Exchange Server 2016 CU23 and/or Exchange Server 2019 CU13/CU14. If you are running Exchange 2016 with anything earlier than CU23, you should update to CU23 immediately. We recommend that Exchange 2019 customers run CU14, but we do still support CU13. If you are running any older versions of Exchange Server (e.g., Exchange 2013 or earlier), you should decommission that infrastructure by either moving to Exchange Online, or by upgrading to Exchange Server 2019 with the latest CU.

To get from Exchange 2016 and Exchange 2019 to Exchange Server SE, there are two types of upgrades that can be performed:

• Legacy upgrade – the traditional way of moving to a new major version of Exchange Server. It requires introducing the newer server into the organization, moving all mailboxes and resources from older servers to new servers and uninstalling the old servers. Legacy upgrades are required when moving from Exchange 2016 to Exchange 2019, from Exchange 2016 to Exchange Server SE. They are also used when moving to new hardware or a later version of Windows Server.
• In-place upgrade – a new way of upgrading to a new version of Exchange Server. It is identical to installing a CU and is available only for upgrades from Exchange 2019 CU14/CU15 to Exchange SE.

In our Exchange Server Roadmap Update we shared a table that lays out the steps needed to get from any version(s) you might be using today, to Exchange Server SE. Here is a slightly updated version of that table:

 

Here is a summary of what you should be doing and when:

 

FAQs

Here are some of the FAQs we’ve heard since the release of our roadmap in May 2024.

Are there any server role, edition, or prerequisite changes in Exchange Server SE RTM?
No. Exchange Server SE RTM will support all the same server roles, editions, and prerequisites as Exchange Server 2019.

Are there any performance, sizing, or architecture guidance changes in Exchange Server SE?
No. Sizing, scaling, and deployment guidance for Exchange Server SE is the same as for Exchange Server 2019.

Are there any features being deprecated or removed from Exchange Server SE?
Yes. We have announced that in Exchange SE CU1, we will remove the following features:

• Support for UCMA 4.0 and the instant messaging feature in Outlook on the web
• Support for Outlook Anywhere (RPC/HTTP) protocol

Why should we upgrade to Exchange Server SE RTM (from earlier versions) if there are no new features?
Exchange Server 2016 and Exchange Server 2019 reach end of support on October 14, 2025. To enable quick and easy in-place upgrades from Exchange Server 2019, we have purposely either pulled new features forward into Exchange Server 2019 CU15 or pushed them to Exchange Server SE CU1 or later, leaving the Exchange SE RTM to be a branding update that introduces new lifecycle and support policies. By moving to Exchange Server SE RTM, your servers are on the supported path to Exchange SE CU1. Once Exchange SE CU1 is released, all older versions will be out of support. We have more features planned after Exchange SE CU1, so Exchange Server development continues.

Can you clarify the license requirements for Exchange Server SE?
Licensing for Exchange Server SE is the same as Exchange Server 2019, with one exception: Microsoft is no longer offering purchases of licenses only (see Microsoft Exchange Server licensing and FAQ for details on the licensing model used by Exchange Server 2019).

For Exchange Server SE, in addition to purchasing the required Server licenses and CALs, customers must also maintain an active subscription. This means purchasing either:

• Cloud subscription licenses for all users and devices that access Exchange Server SE (for example, Microsoft 365 E3 or E5 licenses); or
• Exchange Server SE Server licenses and CALs with Software Assurance (SA).

Other cloud subscription licenses besides Microsoft 365 E3/E5 also satisfy, but we’re calling E3/E5 out because they include Extended Use Rights that provide an unlimited number of Office Server licenses at no additional charge (see the Microsoft Product Terms for full details).

If you don't buy cloud subscription licenses, then Server licenses and CALs you buy must have Software Assurance.

To summarize your licensing options (choose one):

• Qualifying cloud subscription licenses for users (for example, Microsoft 365 E3/E5) If you go this route, all users that access Exchange Server SE must have an E3 or E5 license.
• License (Server and CALs) + SA for Exchange Server 2016/2019 Maintain SA for usage rights and access Exchange Server SE and updates.
• License (Server and CALs) + SA for Exchange Server SE (once released) Maintain SA for Exchange Server SE for usage rights and access to updates.

How do we download Exchange Server SE and obtain our product keys (when available)?
Software products licensed through Volume Licensing (VL) agreements (such as Exchange Server 2019) were previously downloaded from the Volume License Service Center (VLSC).  But the legacy VLSC has been retired and distribution has moved to the Microsoft 365 admin center. Customers who purchase Exchange Server SE (and other VL software) download the product and retrieve their product keys from the Microsoft 365 admin center.  See Administering Volume Licensing Frequently Asked Questions for more information.

Does the name Exchange Server Subscription Edition mean that periodic online license validation is required?
No. As with previous versions of Exchange Server, Exchange Server SE does not perform, or have any requirement for, online license validation. Once a valid Exchange Server SE product key is entered, no additional license checks are performed. You simply need to maintain your subscription (as described above) to stay in license compliance and get access to future Exchange Server SE updates via the Volume License page in the Microsoft 365 admin center.

We have Server licenses and CALs for Exchange Server 2016 without Software Assurance (SA). Why should we buy SA for Exchange Server 2019 and upgrade now, since Exchange 2019 goes out of support in CY2025?
Moving from Exchange 2016 to Exchange 2019 is a legacy upgrade process that requires the introduction of new servers and mailbox moves to the newer version. For organizations running Exchange 2016 today, upgrading to Exchange 2019 now allows you to begin (and complete) your last legacy upgrade before Exchange Server SE is available. You can (and should) start that upgrade now instead of waiting and migrating directly from Exchange Server 2016 to Exchange Server SE. Once on Exchange Server 2019, you can upgrade in-place to Exchange Server SE when it is released. Getting to Exchange 2019 today gives you a lot more time to prepare your organization for Exchange Server SE.

Will Exchange Server SE include a free license for Hybrid servers?
Yes. As with previous versions, Exchange Server SE will continue to provide free licenses for qualified hybrid use via the Hybrid Configuration Wizard (HCW); however, unlike previous versions, you will need to either purchase SA for this license to get Exchange Server updates or have a cloud subscription license that satisfies the requirements. Please note that the Hybrid license is for the purposes of recipient management only. If you host mailboxes or need an Edge Transport server on-premises, you still need an Exchange Server license. See this FAQ. Also as with Exchange 2019, you will be able to use PowerShell and the Exchange Management Tools to manage your recipients without the need for a running Exchange Server, thereby obviating the need for any Hybrid licenses.

Will Microsoft extend the end-of-life date, offer extended support, or offer Extended Security Updates (ESU) for Exchange 2016 or Exchange 2019?
No. We are not extending the end-of-life date for Exchange 2016 or Exchange 2019, and we are not offering extended support or ESU for either version. Our efforts are focused on ensuring that the Exchange Server SE release, as well as the in-place upgrade experience, is seamless for customers running Exchange 2019. We strongly recommend all Exchange Server customers who want to remain on-premises to upgrade to Exchange 2019 as soon as possible.

Will there be a public beta of Exchange Server SE for us to validate in our labs?
No. We will not have a public beta for Exchange Server SE. Customers who are members of our TAP program will get early access to releases of Exchange Server SE. But, as we previously announced, Exchange Server SE RTM will be code equivalent to Exchange 2019 CU15 (plus any SUs released in between). In other words, for all intents and purposes, customers who are not in our TAP program can deploy Exchange 2019 CU15 in their organization and get an early look at how Exchange Server SE RTM will behave.

Will Exchange Server SE allow in-place upgrade of Windows Server operating system while Exchange is already installed?
No. Upgrades of the underlying Windows OS on an Exchange Server are not supported and will remain unsupported. We have heard this request and are evaluating it (but have nothing to announce currently). For customers building new servers, we encourage you to install the newest Windows OS before installing Exchange Server on it (including Windows Server 2025 once Exchange 2019 CU15 is released).

For version coexistence, Exchange Server has always supported N-2 (the current and two previous versions) coexisting in the same organization. Why is this changing with Exchange Server SE?
It’s changing because both Exchange Server 2016 and Exchange Server 2019 reach end of support very soon after Exchange Server SE RTM is released. With the release of Exchange Server SE CU1, Exchange Server SE will be the only supported version, and it will remain that way. Because all other versions are out of support, N-2 no longer applies.
The Exchange Server Team