Exchange Server 2019 and 2016 End of Support: Exchange Online or SE?
In short: Exchange Server 2019 end of support and Exchange Server 2016 end of support came on 14 October 2025; the final ESU updates shipped on 13 October 2026. Exchange Server SE is now the only supported on-premises version. For SMBs that do not want to run servers, the main path is Exchange Online in Microsoft 365.
What does Exchange Server 2019 and 2016 end of support mean?
Support for Exchange Server 2016 and 2019 ended on 14 October 2025 (Microsoft Learn shows 15 October 2025 06:59:59 Pacific Time): no public security updates have been released for either version after October 2025, and Microsoft opens no support cases for them.
The servers keep running, but new vulnerabilities will not be fixed; Microsoft will stop testing Exchange 2016 and 2019 for vulnerabilities after October 2026. The on-premises successor is Exchange Server Subscription Edition (Exchange SE).
| Version | Lifecycle policy | Mainstream end | End of support | Status today |
|---|---|---|---|---|
| Exchange Server 2016 | Fixed | 13 October 2020 | 14 October 2025 | Unsupported; final ESU release 13 October 2026 |
| Exchange Server 2019 | Fixed | 9 January 2024 | 14 October 2025 | Unsupported; final ESU release 13 October 2026 |
| Exchange Server SE | Modern | None | No fixed date; not before 31 December 2035 | Supported; released 1 July 2025 |
Is ESU over, and how long can an old Exchange server stay in use?
Yes, it is over: the final updates of the Exchange 2016/2019 Extended Security Update (ESU) program were released on 13 October 2026, and Microsoft has stated that no further updates will follow. It ran in two periods (October 2025 to 14 April 2026, and May to October 2026), was bought through the Microsoft account team, required an Enterprise Agreement in Period 2 and never extended the support lifecycle.
Exchange Online also reports, throttles and blocks out-of-date on-premises servers:
- Scope: servers that connect to Exchange Online through an inbound connector of type OnPremises, which in practice means hybrid deployments.
- Baseline: since the second week of September 2026, the oldest accepted version for 2016/2019 is the last public update from October 2025. Microsoft says only ESU customers and organizations on Exchange SE will meet the next baseline.
- Stages: 30 days of report-only mode; then mail is delayed with an SMTP 450 error, blocking starts after day 60, and from day 90 no mail is accepted from the server. Each tenant can pause enforcement for up to 90 days per year.
If you migrate through hybrid with a 2016/2019 server, keep the schedule short; on Exchange 2019, the quickest fix is an in-place upgrade to Exchange SE.
Exchange Online or Exchange SE: which path fits your organization?
For SMBs without a team to run servers or a need to keep mailboxes on-premises, Exchange Online removes the server, OS and patching workload; for organizations with a real reason to stay on-premises, Exchange SE is the only supported option. Hybrid is the bridge. To plan email together with network, telephony and endpoint security, see our SMB office IT infrastructure setup guide.
| Criterion | Exchange Online (Microsoft 365) | Exchange Server SE (on-premises) |
|---|---|---|
| Servers and OS | None; Microsoft operates the service | Yours: Windows Server 2019, 2022 or 2025 |
| Updates | Microsoft | Yours: two CUs per year plus security updates as needed |
| Licensing | Per-user subscription | Server licenses and CALs, plus Software Assurance or a qualifying cloud subscription |
| Mailbox size | 100 GB in Business plans and Microsoft 365 E3/E5 | Quota set by the administrator; hardware is the limit |
| Apps using EWS | EWS is being retired; Microsoft Graph required | No change |
| Backup | Organization-level backup is your decision | Server, databases and restores are entirely yours |
| Typical fit | No wish to run servers | Data must stay on own servers; experienced Exchange team |
Exchange Online usually comes within a Microsoft 365 plan. The Business plans (Basic, Standard, Premium) are limited to 300 users in total; Microsoft points larger organizations to enterprise plans. See our Business Basic vs Standard vs Premium guide. For plan contents, see our Microsoft 365 page, Microsoft 365 Business Standard and, beyond 300 users, Microsoft 365 E3. Backup still needs its own plan, as our Microsoft 365 backup article explains.
How do you move to Exchange SE, and which licenses does it need?
Exchange Server SE is the new name of on-premises Exchange: released on 1 July 2025, it follows the Modern Lifecycle Policy, with no new year-numbered versions to come. The RTM build is code-equivalent to Exchange 2019 CU15.
| Version in use today | Path recommended by Microsoft |
|---|---|
| Exchange 2019 CU14 / CU15 | In-place upgrade; identical to installing a CU, DAG members included |
| Exchange 2019 CU13 or earlier | Update to CU15 first, then upgrade in place |
| Exchange 2016 CU23 | Legacy upgrade: add an SE server and move mailboxes; do not install new Exchange 2019 servers |
| Exchange 2016 CU22 or earlier | Update to CU23 first, then legacy upgrade |
Per Microsoft's 22 May 2026 update, SE CU1 is expected in the second half of 2026 and CU2 in the first half of 2027; CU2 Setup will be blocked wherever Exchange 2016 or 2019 servers remain. Exchange SE runs on Windows Server 2019, 2022 and 2025; Microsoft recommends Server Core and does not support in-place OS upgrades under Exchange.
Licensing requires an active subscription on top of server licenses and CALs: qualifying cloud subscriptions for all users who access SE (Microsoft cites Microsoft 365 E3/E5) or Software Assurance. There is no online license validation, and Microsoft lists 31 December 2035 as the earliest possible end of support.
Exchange 2016 is only supported on Windows Server 2012, 2012 R2 and 2016; the first two are already out of support and Windows Server 2016 follows on 12 January 2027. See our Windows Server 2016 migration plan to handle both as one project. For servers that stay on-premises, consider a server maintenance agreement whose scope is defined in the contract.
Cutover, express or hybrid: which Exchange Online migration method should you use?
Source version and mailbox count decide: Microsoft recommends cutover or express for under 150 mailboxes moved in a few days, and Exchange hybrid for more mailboxes or a gradual move. Staged migration applies only to Exchange 2003 and 2007.
| Method | When Microsoft recommends it | How it works |
|---|---|---|
| Cutover | Exchange 2003 or later; fewer than 2,000 mailboxes, 150 or fewer recommended | Mailboxes, contacts and groups in one batch over Outlook Anywhere; directory sync must be off |
| Express (minimal hybrid) | Documented for Exchange 2010, 2013 and 2016; a move finished within a few weeks | Users are synced once with Microsoft Entra Connect, then sync is turned off |
| Exchange hybrid (full) | Exchange 2013 or later; more than 150 mailboxes or a gradual move | Shared address book, calendar availability, mailbox moves in both directions; ongoing directory sync |
| IMAP | Exchange 2000 or earlier, or other mail systems | Email only; contacts and calendars are not moved |
| PST import | Large PST files | Network upload or drive shipping |
Two conditions apply to hybrid today. Since 31 October 2025, calendar availability and MailTips require the dedicated Exchange hybrid application in Entra ID, supported on Exchange SE and on Exchange 2016 CU23 and 2019 CU14/CU15 with at least the April 2025 Hotfix Update. And the enforcement described above hits hybrid servers directly.
Microsoft notes that forwarding settings are not migrated; explicit Full Access, Send As, Send on Behalf and folder permissions are, inherited ones are not.
How do you plan an Exchange Online migration step by step?
A solid migration starts with an inventory and ends with the old server safely retired. The checklist and steps below condense Microsoft's cutover and hybrid documentation for SMBs.
| What to collect | Why it matters |
|---|---|
| Mailbox count, total and average size | Method choice and time estimate |
| Shared and resource mailboxes, public folders | Licensing and move order differ |
| Forwarding rules and mailbox permissions | Forwarding is not migrated; related mailboxes move in the same batch |
| Devices and apps sending mail via SMTP (multifunction printers, ERP) | They must be reconfigured when the mail path changes |
| Apps using EWS | Exchange Online requires Microsoft Graph support |
| Exchange version, CU level, certificate | Cutover and hybrid prerequisites |
- Finish the inventory and pick the target: Exchange Online, Exchange SE, or hybrid during transition.
- Plan licenses: every user mailbox in Exchange Online needs a license; a shared mailbox can be used without one up to 50 GB.
- Verify your domain in Microsoft 365 (TXT record).
- Before migrating, lower the MX record TTL to 3,600 seconds or less, as Microsoft recommends.
- Pilot with two or three users, then move batches that keep permission-linked mailboxes together.
- Point the MX record to Microsoft 365; recognition can take up to 72 hours, so do not delete the cutover batch earlier.
- Create the Autodiscover CNAME record and assign licenses; an unlicensed mailbox is disabled when the 30-day grace period ends.
- Set up security: follow our Microsoft 365 security settings checklist for MFA and Conditional Access, and check SPF, DKIM and DMARC with our email security tool.
- Retire the old server: after a cutover, Exchange can be uninstalled once the on-premises organization is no longer needed. In hybrid with ongoing directory sync, shut the last server down instead of uninstalling it, and manage recipients with Exchange 2019 CU12+ management tools or from the cloud after a source-of-authority transfer.
Estimate a lower bound for duration: minimum transfer time ≈ total data to move ÷ real upload bandwidth available for the migration (same units). Microsoft notes that performance varies with network, mailbox size and migration speed, so refine it with the rate measured in the pilot.
We can start from an inventory of your Exchange environment to settle method, licenses and schedule. Get a Quote
FAQ
Did my Exchange 2016 or 2019 server stop working when support ended?
No. According to Microsoft, Exchange 2016 and 2019 keep functioning after 14 October 2025 as before. But the final ESU updates shipped on 13 October 2026, so later vulnerabilities stay open, and out-of-date servers sending mail to Exchange Online over a hybrid connector can be throttled and blocked.
Can I move directly from Exchange 2016 to Exchange SE?
Yes, but not in place. You add an Exchange SE server to the Exchange 2016 CU23 organization, move the mailboxes and remove the 2016 servers before SE CU2, expected in the first half of 2027, because CU2 Setup will block coexistence with older versions.
Which licenses does Exchange SE require?
Besides server licenses and CALs, you need qualifying cloud subscriptions for all users who access SE, or Software Assurance. The hybrid license issued by the Hybrid Configuration Wizard covers recipient management only; a server hosting mailboxes or acting as an SMTP relay needs its own Exchange Server license.
How large are mailboxes in Exchange Online?
Per the Exchange Online limits on Microsoft Learn (updated 7 April 2026), user mailboxes are 100 GB in Business Basic, Standard, Premium and Microsoft 365 E3/E5. Archives are 50 GB in Basic and Standard, and reach 1.5 TB with auto-expanding archiving in Premium and E3/E5.
Will our apps that use EWS be affected?
Yes, once mailboxes move to Exchange Online. Under Microsoft's plan, EWS in Exchange Online is being disabled tenant by tenant from 1 October 2026 and shuts down fully on 1 April 2027; Exchange Server is unaffected. Find dependent apps with the EWS usage reports and ask vendors for Microsoft Graph support.
Which Microsoft 365 plan should we choose for Exchange Online?
User count and security needs decide: Business plans are limited to 300 users in total, and Microsoft points larger organizations to enterprise plans. To work out the right license mix from your mailbox count and sizes, you can use our quote request form.
Conclusion
- Exchange 2016 and 2019 are unsupported; ESU updates ended with the final release on 13 October 2026.
- If you stay on-premises, the target is Exchange SE: in place from 2019, via a new server from 2016.
- If you do not want to run servers, move to Exchange Online: cutover up to 150 mailboxes (express also on 2016), hybrid above that.
- Inventory EWS apps, SMTP-sending devices and mailbox permissions first.
Sora Yazılım Teknolojileri, an Istanbul-based technology company, provides Microsoft 365 selection, procurement, deployment and support, plus a server maintenance agreement (scope defined in the contract) for on-premises servers. In a free discovery call we can review your Exchange environment and options together; see our About us page.
Get a Quote · WhatsApp: WhatsApp Support · Phone: +90 544 785 21 87 · Email: talep@sorayazilim.com
Sources
- Exchange lifecycle pages — Microsoft Learn. learn.microsoft.com · learn.microsoft.com · learn.microsoft.com · learn.microsoft.com (accessed 19 October 2026)
- Exchange SE availability and upgrade guidance (updated 22 May 2026) — Exchange Team Blog. techcommunity.microsoft.com · techcommunity.microsoft.com (accessed 19 October 2026)
- ESU announcements and October 2026 Security Updates — Exchange Team Blog. techcommunity.microsoft.com · techcommunity.microsoft.com · techcommunity.microsoft.com (accessed 19 October 2026)
- Throttling and blocking of vulnerable Exchange servers (2023, 2026) — Exchange Team Blog. techcommunity.microsoft.com · techcommunity.microsoft.com (accessed 19 October 2026)
- Migration path, cutover and minimal hybrid guides — Microsoft Learn. learn.microsoft.com · learn.microsoft.com · learn.microsoft.com · learn.microsoft.com (accessed 19 October 2026)
- Exchange hybrid, dedicated hybrid app, management tools — Microsoft Learn. learn.microsoft.com · learn.microsoft.com · learn.microsoft.com (accessed 19 October 2026)
- Exchange Online limits (updated 7 April 2026) — Microsoft Learn. learn.microsoft.com (accessed 19 October 2026)
- Exchange Online EWS, Your Time is Almost Up — Exchange Team Blog, 2026. techcommunity.microsoft.com (accessed 19 October 2026)
- Exchange supportability matrix, Windows Server 2016 lifecycle, Business Premium FAQ — Microsoft Learn. learn.microsoft.com · learn.microsoft.com · learn.microsoft.com (accessed 19 October 2026)
How this article was prepared
Prepared by: Sora Yazılım Team. This article was prepared with AI assistance; technical details were checked against the vendor and official sources linked in the text as of 19 October 2026.
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