Exchange Server Roadmap Update

[ScottSchnoll]

Today, we are providing an update on our product roadmap for Microsoft Exchange Server, and our next milestones in the Exchange Server journey to support the specific needs of our on-premises customers, hosted services providers, and other partners. Here’s what’s ahead:

• We will release one final Cumulative Update (CU) for Exchange Server 2019—the 2024 H2 CU aka CU15—later this year.
• We will release Exchange Server Subscription Edition (Exchange Server SE) early in the third quarter of calendar year 2025.
• We will release the first CU for Exchange Server SE—CU1—in late 2025.

Exchange Server 2019 CU15

CU15 will introduce new features and changes to support the RTM release of Exchange Server SE.

New Features in CU15

• Adding support for Transport Layer Security (TLS) 1.3.  TLS 1.3 eliminates obsolete cryptographic algorithms, improves security over older versions, and aims to encrypt as much of the handshake as possible.
• Reintroducing certificate management in the Exchange admin center (EAC). Admins can create a request for a new certificate, complete the request after receiving the certificate from their provider, export certificates as PFX files, and import certificates from PFX files.

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).

Additional changes expected in CU15 include:

• The Windows MSMQ component will no longer be installed by Setup
• Improvements in Exchange Server AMSI integration
• Adding PDF files to Exchange Server CBC encryption support.

Exchange Server Subscription Edition

Exchange Server SE, the next release of Microsoft Exchange Server, will be available for download from the Microsoft 365 admin center (previously the Microsoft Volume License Service Center) in the early part of Q3 of 2025.  The licensing model used by Exchange Server SE is the same as SharePoint Server Subscription Edition, which requires subscription licenses or licenses with active Software Assurance for server and user licenses. We will continue to provide a free Hybrid server license and key, which will continue to be distributed using the Hybrid Configuration Wizard.

The hardware and operating system requirements for Exchange Server SE are the same as Exchange 2019 CU15, which adds support for Windows Server 2025.

The RTM release of Exchange Server SE will not require any changes to Active Directory when upgrading from Exchange Server 2019. There are no Active Directory schema changes beyond those in Exchange Server 2019, and we will continue to support the Windows Server 2012 R2 forest functional level.

Finally, Exchange Server SE will be supported under the modern lifecycle support policy.

Release Details

To allow for rapid adoption and deployment, the RTM release of Exchange Server SE will be code equivalent to (e.g., the same exact code as) Exchange Server 2019 CU15, except for the following changes:

• The License agreement, an RTF file shown only in the GUI version of Setup, will be updated.
• The name will change from Microsoft Exchange Server 2019 to Microsoft Exchange Server Subscription Edition.
• The build and version number will be updated.

Please note that:

• If any Security Updates (SUs) are released before CU15, those updates will be incorporated into CU15.
• If any SUs are released after CU15, then the RTM release of Exchange Server SE will be code equivalent to Exchange 2019 CU15 plus the latest SU. If you are on CU15, which is where you should be, then you should also be already running the latest SU released after CU15, thereby maintaining code equivalence with the RTM release.

Upgrading to Exchange Server SE from Previous Versions

To help further accelerate in-place upgrades, in addition to being code equivalent, Exchange Server SE will support two types of upgrades: in-place upgrade and legacy upgrade.

In-place upgrade

The fastest and easiest way to get from Exchange Server 2019 to Exchange Server SE is to perform an in-place upgrade. The upgrade experience is identical to installing a CU. Once a server is running Exchange Server SE, it will be updated with our update cadence of two CUs per year (in H1 and H2).

Legacy upgrade

Exchange Server SE also supports legacy upgrades, which involve building out a new infrastructure and moving namespaces and mailboxes to that new infrastructure. Some of these processes are used in other scenarios, such as when replacing server hardware or when you want to use a newer version of Windows Server, and those processes continue to be supported in Exchange Server SE.

If your organization is running Exchange 2016 today and you want to continue to run Exchange on-premises, then you have at least one more legacy upgrade to do.

To ensure a timely move from Exchange 2016 to Exchange Server SE, we recommend doing a legacy upgrade now from Exchange 2016 to Exchange 2019 as soon as possible. Once you are running Exchange 2019, you can do a quick and easy in-place upgrade to Exchange Server SE.

Update Paths for Exchange 2019 CU15 and Exchange Server SE

As with all previous versions, Exchange Server SE can be used to create a new Exchange on-premises organization from scratch and/or can coexist in an Exchange organization that includes only supported versions (e.g., Exchange 2016 CU23 and/or Exchange 2019 CU14 or later). It cannot be introduced into an Exchange organization with unsupported versions.

Below is a table that summarizes the available paths based on the version(s) you’re running:

Version in use	Exchange 2019 CU15	Exchange Server Subscription Edition (SE)
Exchange Server 2013	Not supported in the organization. Legacy upgrade to Exchange 2019 CU14 now, remove Exchange 2013, and update to Exchange 2019 CU15 when available.	Not supported in the organization. Legacy upgrade to Exchange 2019 CU14 now. Remove Exchange 2013, update to CU15 when available and in-place upgrade to Exchange Server SE when available.
Exchange Server 2016 CU23	Legacy upgrade to Exchange 2019 CU14 now and update to CU15 when available.	Legacy upgrade to Exchange 2019 CU14 now or CU15 when available, and in-place upgrade to Exchange Server SE when available.
Exchange Server 2016 CU22 and earlier	Not supported in the organization. Legacy upgrade to Exchange 2019 CU14 now and update to CU15 when available; or update to Exchange 2016 CU23 now, and then legacy upgrade to Exchange 2019 CU15 when available.	Not supported in the organization. Update to Exchange 2016 CU23 and legacy upgrade to Exchange 2019 CU14/CU15, then in-place upgrade to Exchange Server SE when available.
Exchange Server 2019 CU14 and later	Update CU14 servers to Exchange 2019 CU15 when available.	In-place upgrade to Exchange Server SE.
Exchange Server 2019 CU13	Update to Exchange 2019 CU14 now and update to CU15 when available.	Not supported in the organization. Update to Exchange Server 2019 CU14/CU15, then in-place upgrade to Exchange Server SE.
Exchange Server 2019 CU12 and earlier	Not supported in the organization. Update to Exchange 2019 CU14 now and update to CU15 when available.	Not supported in the organization. Update to Exchange Server 2019 CU14/CU15, then in-place upgrade to Exchange Server SE.

Table 1 - Update paths to Exchange Server 2019 CU15 and Exchange Server SE

Exchange Server SE CU1

Exchange Server SE will be serviced with the existing cadence of two CUs per year. In October 2025, we expect to release Exchange Server SE CU1. Exchange Server SE CU1 is expected to introduce the following changes:

• Kerberos for server-to-server communication
• Adding support for an Admin API and deprecating RPS
• Removing Outlook Anywhere
• Removal of support for co-existence with earlier versions
• Updating the Visual C++ redistributable to the version that ships with Visual Studio 2022
• Removal of support for UCMA 4.0 and the instant messaging feature in Outlook on the web

Kerberos for server-to-server communication

The default authentication protocol used for communication between Exchange servers will use Kerberos instead of NTLMv2. In CU1, Setup will enable Kerberos (specifically, auth = Negotiate:Kerberos) on all Exchange server virtual directories on the server being installed.

Admin API and RPS deprecation

The Admin API, a set of REST-based APIs to enable remote management of Exchange servers will be introduced. Remote PowerShell (RPS) protocol will be supported in CU1 but deprecated in future CUs. This is not about deprecating the PowerShell management, rather, modernizing the protocol used between the PowerShell client and server.

Removing Outlook Anywhere

Exchange Online and Microsoft 365 removed support for Outlook Anywhere (aka RPC over HTTP) several years ago and starting in CU1, Outlook Anywhere will be removed from Exchange Server SE. This change may affect any third-party Outlook add-ins that still use this protocol.

Removal of support for co-existence with all previous versions

At the time CU1 is released, Exchange Server SE will be the only supported version. As all previous versions will be unsupported at that time, Setup in CU1 will block coexistence with anything other than Exchange Server SE RTM or later.

Call to Action

Move to Exchange Server 2019 CU14 today:

• If you want to run Exchange Server, move to Exchange Server 2019 CU14 on Windows Server 2022 today.
• If you prefer to wait for Windows Server 2025, move to Exchange Server 2019 CU15 as soon as the new operating system is available.

If you are running Exchange Server 2019, keep your Exchange servers updated by always running a supported CU and the latest SU and the latest updates for the Windows operating system, and regularly run the Exchange Health Checker.

Because Windows Server 2019 reaches end of life in January 2029, new deployments of Exchange Server 2019 CU15 and Exchange Server SE RTM are recommended to be installed on Windows Server 2022, or when available, Windows Server 2025.

FAQs

Q: Exchange Server SE is being released very shortly before my current version (Exchange 2016 or Exchange 2019) reaches its end of life; how can I upgrade in time?

A: Our approach to the RTM release of Exchange Server SE enables you to upgrade more rapidly than previous releases. We recommend all customers then perform an in-place upgrade from Exchange 2019. This is the fastest and easiest way to get from Exchange 2019 to Exchange Server SE, and the experience is identical to installing a CU.

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Q: Will Microsoft extend the end-of-life date, offer extended support, or offer Extended Security Updates (ESU) for Exchange 2016 or Exchange 2019?

A: 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 2016 customers who want to remain on-premises to upgrade to Exchange 2019 as soon as possible.

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Q: I am moving from Exchange 2016 to Exchange 2019 as Microsoft recommends, and I plan to do an in-place upgrade to Exchange Server SE when it is available. Should I deploy CU14 on Windows Server 2022 now or wait until later this year and deploy CU15 on Windows Server 2025 RTM?

A: Windows Server 2022 and Windows Server 2025 (when released) are supported operating systems for Exchange Server 2019 CU15 and Exchange Server SE, and as far as Exchange is concerned, there is no difference in Windows Server feature or component usage. The primary difference from an Exchange server perspective is the lifecycle, where Windows Server 2025 reaches end of life a few years after Windows Server 2022.