Microsoft has told customers it will begin blocking the Exchange Web Services (EWS) API by default on October 1, 2026, with a final shutdown slated for April 1, 2027, while offering temporary workarounds IT teams can use until that final date.
October 1, 2026 and April 1, 2027: the shutdown timeline
The company announced in February that October 1, 2026 is the start of the default block for EWS in Exchange Online, and that administrators will be able to temporarily maintain access via an app allowlist until the API’s final shutdown on April 1, 2027. "We are now in the first stage of EWS disablement, where customers are still able to re-enable EWS. Re-enabling EWS will stop working in April 2027," Microsoft said.
Which apps are affected
EWS is the API used to access Exchange mailbox items—email messages, meetings and contacts—in both Exchange Online and on-premises servers. Microsoft lists a range of clients and integrations that rely on EWS, including:
- Outlook desktop add-ins
- Older versions of Outlook for Windows
- Apple Mail and Calendar on macOS
- Various other applications that integrate with Exchange mailboxes
When EWS is disabled in a tenant, affected applications can show errors ranging from alerts that the EWS protocol is unavailable to repeated prompts to enter username or password.
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Get a security leadHow administrators can re-enable EWS today
Microsoft describes two immediate mechanisms tenant administrators can use to restore EWS access in Exchange Online while the temporary window remains open.
- Microsoft 365 admin center: In Baseline Security Mode, uncheck the option labeled "Block your entire organization from using EWS" on the Baseline Security Mode page.
- Exchange Online PowerShell: Run the command Set-OrganizationConfig -EWSEnabled $true; Microsoft says this should re-enable EWS within four hours.
Those options are temporary: re-enabling EWS will cease to be possible when Microsoft completes the shutdown in April 2027.
Microsoft’s recommended long-term solution: move off EWS to Microsoft Graph
Microsoft has made clear that the permanent fix is to stop using the EWS API. "The long-term solution is to update your applications to the application versions that do not use EWS," the company said. It advised administrators to contact application vendors for updated versions, or, for in-house software, to change the code so it no longer depends on EWS.
For developers, Microsoft recommends migrating to the Microsoft Graph API, noting that Graph "has near-complete feature parity with EWS for most scenarios." The company also emphasized that the EWS retirement affects only Microsoft 365 and Exchange Online environments; the API will continue to work in on-premises Exchange Server installations.
How app developers, tenant administrators, and enterprises should respond
App developers: Microsoft’s guidance is direct—replace EWS calls in your code or ship updated application versions that use Microsoft Graph, since EWS will stop functioning in Exchange Online after April 1, 2027.
Tenant administrators and IT teams: You can temporarily restore functionality by unchecking "Block your entire organization from using EWS" in Baseline Security Mode or by running Set-OrganizationConfig -EWSEnabled $true in Exchange Online PowerShell; Microsoft says the change through PowerShell should propagate within four hours.
Enterprises and procurement leaders: If third‑party software in your environment relies on EWS, the vendor must provide an updated version that does not use EWS, or you must plan for in‑house code changes ahead of the April 2027 cutoff.
Microsoft’s sequence of notices stretches back several years: a 2018 warning that EWS would stop receiving functionality updates, a September 2023 announcement that shutdown activity would begin in October 2026, and an earlier pruning in October 2021 when Microsoft deprecated the 25 least‑used EWS Exchange Online APIs and removed support for them in March 2022 for security reasons. For organizations still depending on EWS, the choice is now a short term restoration versus a longer-term migration to Microsoft Graph—one that vendors and internal developers must execute before April 1, 2027.
