Microsoft has provided a path for Exchange Online administrators to restore access to the retired Exchange Web Services (EWS) API, addressing disruptions to dependent applications that lost connectivity when the service was disabled.
EWS functions as an API enabling third-party software to interact with Exchange mailbox data, including messages, calendar events, and contact information across both Exchange Online and on-premises Exchange deployments. The API powers integrations in Outlook desktop extensions, legacy Outlook for Windows builds, Apple Mail and Calendar on macOS, and numerous other applications.
Microsoft announced in February that it would begin blocking EWS by default starting October 1, 2026, with a final termination date of April 1, 2027. Organizations can maintain temporary access through an application allowlist during this transition window. When EWS access is blocked, affected applications display protocol unavailability errors or repeatedly request credential re-entry.
Restoring EWS Access
To restore functionality for broken EWS applications, tenant administrators have two methods available. The first involves accessing the Microsoft 365 admin center, navigating to Baseline Security Mode, and unchecking the "Block your entire organization from using EWS" setting. Alternatively, administrators can execute the Set-OrganizationConfig -EWSEnabled $true command through Exchange Online PowerShell, with changes taking effect within 4 hours.
Microsoft emphasized the temporary nature of this remediation: "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."
Long-Term Migration Path
The company stressed that re-enabling EWS serves only as a stopgap measure. According to Microsoft, "The long-term solution is to update your applications to the application versions that do not use EWS. You must contact your application vendor to get the updated application version, or if you created the application yourself, you must change the code to not use EWS anymore."
For developers still relying on EWS, Microsoft recommends migrating to the Microsoft Graph API before the April 2027 deadline. The Graph API provides near-complete feature parity with EWS across most use cases.
The retirement initiative applies exclusively to Microsoft 365 and Exchange Online environments. On-premises Exchange Server installations will continue supporting EWS without interruption.
Timeline of EWS Deprecation
The EWS shutdown represents the culmination of a multi-year deprecation cycle. Microsoft first signaled the API's decline in 2018 when it halted new feature development. In October 2021, the company deprecated 25 of the least-used EWS Exchange Online APIs and removed support for them in March 2022 citing security concerns. The formal retirement announcement came in September 2023, establishing the October 2026 blocking date and April 2027 final termination.