Microsoft Provides Fix for Broken Exchange Online EWS Apps After API Disablement

EWS API Disablement and App Failures

Microsoft began disabling the Exchange Web Services (EWS) API, leading to various applications that rely on it to stop functioning. These affected applications include Outlook desktop add-ins, older versions of Outlook for Windows, and Apple Mail/Calendar on macOS, which displayed errors such as protocol unavailability or repeated login prompts.

Temporary Re-enablement Options

To resolve immediate issues, Microsoft has provided two methods for tenant administrators to re-enable EWS. The first method involves unchecking 'Block your entire organization from using EWS' on the Baseline Security Mode page within the Microsoft 365 admin center. Alternatively, administrators can use Exchange Online PowerShell to execute the command 'Set-OrganizationConfig -EWSEnabled $true', which typically re-enables EWS within four hours.

Long-Term Solution and Migration

While re-enabling EWS offers a temporary fix, this option will no longer be available after April 2027. Microsoft emphasizes that the permanent solution requires updating applications to versions that do not use EWS. Application vendors should provide updated versions, and developers who created their own applications must modify their code to transition away from EWS.

Microsoft advises app developers to switch to the Microsoft Graph API, which offers feature parity with EWS for most common scenarios. This migration is crucial as the EWS API will be fully retired from Microsoft 365 and Exchange Online environments.

Context and Scope of Retirement

The retirement of EWS in Exchange Online follows a 2018 warning about the API no longer receiving functionality updates and a September 2023 announcement of its planned shutdown starting October 2026. This retirement process exclusively impacts Microsoft 365 and Exchange Online; the EWS API will continue to function in on-premises Exchange Server installations.