Exchange Server Subscription Edition (SE): Licensing & Upgrade

This is a reference page our Exchange Server support team maintains on Exchange Server Subscription Edition (SE): what it is, how the licensing works, and how to get there from 2016 or 2019.

What is Exchange Server Subscription Edition

Exchange Server SE is the current — and only supported — version of on-premises Exchange Server. It reached Release to Manufacturing (RTM) and general availability on July 1, 2025. Support for Exchange Server 2016 and Exchange Server 2019 ended on October 14, 2025; Microsoft confirmed both dates on the Exchange Team blog. There will be no Exchange Server 2028 or any other year-numbered release. SE replaces the major-version model with a single continuously serviced product, updated through cumulative updates.

SE is not a cloud product and not a rewrite. Per the official What's new in Exchange Server SE documentation, SE RTM is code equivalent to Exchange Server 2019 CU15 with exactly three changes: a new license agreement, the product name (Microsoft Exchange Server Subscription Edition), and the build number. New features begin with SE CU1, not at RTM.

What changed from Exchange 2019

• Code: nothing at RTM. Same binaries as 2019 CU15 apart from name, EULA, and build number. Feature changes start in SE CU1.
• System requirements: same as Exchange 2019 — the two versions share one system requirements page. Windows Server 2019 or later for the Mailbox role; existing 2019 hardware carries over.
• Licensing: the significant change. Perpetual-only licensing is gone; an active subscription or Software Assurance is required (details below).
• Servicing: no more major versions. SE receives cumulative updates and security updates indefinitely under the Modern Lifecycle Policy, with no fixed end-of-support date.
• Coexistence: SE RTM setup blocks coexistence with Exchange 2013. SE CU2 setup will block coexistence with any version out of support at its release — which means 2016 and 2019.

Exchange Server SE licensing requirements

The license structure is unchanged from Exchange 2019: a server license per server (Standard or Enterprise edition) plus a Client Access License (CAL) per user or device (Standard CAL, with an additive Enterprise CAL for compliance features). What changed is the purchase model. Exchange SE cannot be bought as a one-time perpetual license without coverage. To run it compliantly, one of the following must be true:

• Active Software Assurance on existing Exchange Server and CAL licenses. Customers with SA on Exchange 2019 licenses upgrade to SE at no additional cost for the duration of the SA term, using the existing 2019 product key at RTM.
• Subscription licenses for Exchange SE server and CALs, purchased through Volume Licensing. SE entered the EA, MPSA, and Open Value price lists in August 2025. Microsoft raised prices effective August 1, 2025: roughly 10% on server licenses, 15% on Core CAL Suites, and 20% on Enterprise CAL Suites.
• A qualifying Microsoft 365 subscription such as E3 or E5, which carries on-premises server use rights. This is also how SE rights are delivered in CSP — there is no standalone SE SKU in that channel.

Perpetual Exchange 2019 licenses without SA grant no rights to SE, and SA cannot normally be added retroactively; those organizations buy new subscription licenses. Full terms are on Microsoft's Exchange licensing FAQ. On product keys: SE RTM accepts existing Exchange 2019 keys, but Microsoft has documented a new key requirement in a future CU, so key management does not end at the upgrade.

Upgrade paths to Exchange Server SE

Microsoft's upgrade documentation defines two methods. Which one applies depends entirely on the starting version.

Why the in-place upgrade is low risk

Because SE RTM is code equivalent to 2019 CU15, the in-place upgrade is functionally a cumulative update install, not a version migration. The Exchange Team published a dedicated post, Why in-place upgrade from Exchange 2019 to Exchange SE is low risk, making this point. DAG members upgrade the same way they take CUs; standard CU practices apply — put the server in maintenance mode, upgrade, validate, move on. The same discipline applies afterward: our Exchange cumulative update guide covers the CU installation process that now defines SE servicing.

The 2016 path

Exchange 2016 requires the legacy route: new servers, mailbox moves, decommission. Exchange 2016 CU23 coexists with SE in the same organization, so the migration can run directly to SE without an interim 2019 deployment. The deadline pressure is SE CU2 — after it ships, SE setup will refuse to install into an organization that still contains 2016 or 2019 servers. Organizations still on 2016 should complete coexistence-based migration before then.

Servicing model going forward

Exchange SE is governed by the Modern Lifecycle Policy: it stays supported as long as customers keep current with cumulative updates and maintain their subscription or SA. Microsoft's stated cadence is two CUs per year, with security updates and hotfix updates in between as needed. Build numbers for every SE release are tracked on the official build numbers and release dates page. The practical consequence: staying on an old CU is no longer a slow drift toward a distant end-of-support date — falling behind on CUs is itself what takes a server out of support.

Hybrid and coexistence notes

• Hybrid deployments with Microsoft 365 are fully supported on SE, same as 2019. After an in-place upgrade, re-run the Hybrid Configuration Wizard to refresh connectors and OAuth.
• Recipient management: organizations that migrated all mailboxes to Exchange Online but still sync identities from Active Directory keep at least one Exchange server for recipient management — that server should now be SE, or be replaced by the Exchange Management Tools-only approach where it fits.
• DAGs: no changes. SE servers cannot join a DAG with 2019 members (standard cross-version rule), so in-place upgrades roll through the DAG node by node.
• Edge Transport: upgrade Edge servers as part of the same effort; re-create the Edge subscription against SE Mailbox servers after a legacy upgrade.

What running Exchange 2016 or 2019 today means

The decision tree is short. If mailboxes can move to Exchange Online, that removes the servicing burden entirely. If on-premises Exchange stays — for regulatory, data-residency, or dependency reasons — SE is the only supported destination, and for 2019 CU14/CU15 servers the upgrade is a CU-sized change, not a project.

FAQ

When was Exchange Server SE released?

July 1, 2025. That is the RTM and general availability date. It went into Volume Licensing price lists in August 2025.

Is Exchange Server SE the last version of Exchange Server?

It is the last major version. There will be no year-numbered successors. SE continues indefinitely through cumulative updates under the Modern Lifecycle Policy.

Does Exchange Server SE require a subscription?

Yes, in one of three forms: active Software Assurance on Exchange server and CAL licenses, Exchange SE subscription licenses, or a qualifying Microsoft 365 subscription (E3/E5) with on-premises use rights. There is no perpetual-only option.

Can I upgrade in place from Exchange 2019 to SE?

Yes, from Exchange 2019 CU14 or CU15. The process is identical to installing a cumulative update — same hardware, same operating system, no mailbox moves.

Can I upgrade in place from Exchange 2016 to SE?

No. Exchange 2016 requires a legacy upgrade: install SE on new servers in the same organization (2016 CU23 coexists with SE), move mailboxes, then decommission the 2016 servers.

Do I need a new product key for Exchange SE?

Not at RTM — existing Exchange 2019 keys work. Microsoft has stated a new product key requirement arrives in a future cumulative update.

Is Exchange 2019 still supported?

No. Support for Exchange 2016 and 2019 ended October 14, 2025. Only organizations enrolled in the paid ESU program receive security updates, starting with the December 2025 releases.