What Exchange Server SE is
Exchange Server Subscription Edition (SE) is the successor to Exchange Server 2019. At launch it was deliberately identical in code to Exchange 2019 CU15 — the point of the first release was the change of licensing model, not new features. New features start arriving in later cumulative updates.
The important change is the lifecycle. Instead of a fixed support end date ten years out, SE follows Microsoft’s Modern Lifecycle Policy: it stays supported as long as you keep it current and keep paying for the subscription. There is no longer a version you buy once and run for a decade.
How Exchange Server SE is licensed
You still need server licences (Standard or Enterprise edition) and client access licences, as before. On top of that, Microsoft requires an active subscription, which means one of:
- Cloud subscription licences for every user and device that accesses Exchange Server SE — Microsoft calls out Microsoft 365 E3 and E5, which also include rights that cover the server licences.
- Exchange Server SE server licences and CALs with Software Assurance, kept current for as long as you run it.
Organisations that bought Exchange 2019 outright, without Software Assurance, are the ones most surprised by this: they need new licensing as well as an upgrade.
Why it costs more than Exchange 2019 did
From 1 July 2025 Microsoft increased the price of its on-premises server products, Exchange Server SE among them, by 10%. Client access licence suites rose further: 15% for the Core CAL Suite and 20% for the Enterprise CAL Suite. Microsoft does not publish a UK price list for these; you buy through a licensing partner, and the price depends on your agreement type and volume.
The running costs nobody quotes you
The licence is rarely the largest cost of running Exchange yourself. The rest of the bill:
- Servers and storage — at least two servers if you want resilience, plus the storage for every mailbox and its copies.
- Windows Server licences for those servers.
- Backup software and somewhere off-site to keep the backups.
- Email filtering, because Exchange’s built-in protection is basic.
- Certificates for Outlook on the web, Autodiscover and ActiveSync, renewed on schedule.
- Administration time: cumulative updates, monthly security updates, monitoring, and the out-of-hours call when a database will not mount.
- The cost of being late with a patch. Exchange is internet-facing by design and has been heavily targeted; an unpatched Exchange server is one of the most attacked machines a business can own.
The upgrade paths
- Exchange 2019 CU14 or CU15 can be upgraded in place — Microsoft describes it as being like installing a cumulative update.
- Exchange 2019 CU13 or earlier must be brought up to CU14 or CU15 first.
- Exchange 2016 cannot be upgraded in place. It needs a “legacy” upgrade: install an SE server alongside it, move the mailboxes, then decommission 2016 — which Microsoft requires before Exchange SE CU2, planned for the first half of 2027.
- Exchange 2013 or earlier cannot coexist with SE at all; it needs an intermediate migration or a move to another platform.
Who should run Exchange Server SE
SE makes sense for organisations with a genuine requirement to keep mail on their own infrastructure — a regulatory or contractual obligation, an air-gapped environment, an integration that cannot move — and an Exchange-literate team to run it. If that is you, SE is a sound, supported platform.
For most UK SMEs it is the most expensive way to keep doing the same thing. If what you want is Exchange — Outlook, shared calendars, public folders, delegate access — without the servers, there are two cheaper routes: Microsoft 365, or hosted Exchange, where a provider runs Exchange Server SE for you and you pay per mailbox.
Hosted Exchange: SE without the servers
That is what we do. MyExchangeServer runs Exchange Server SE in UK data centres and handles the licensing, patching, backups, filtering and certificates. You pay £8.00 + VAT per 50 GB mailbox per month, with no minimum term, and your own team keeps administrative control through the SolidCP control panel. Coming from Exchange 2016 or 2019, the move is Exchange to Exchange — the cleanest kind of migration there is — and we do it for free.
One thing to know before you choose any SE-based service, including ours: the new Outlook for Windows does not yet support on-premises Exchange, so your team will use classic Outlook, which Microsoft supports until at least 2029. Our guide to the new Outlook and Exchange Server explains.