Microsoft shares how to fix broken Exchange Online EWS apps

Microsoft says IT admins can re-enable the retired Exchange Web Services (EWS) API in Exchange Online to fix EWS apps that have stopped working.

EWS is an API for developing apps that can access Exchange mailbox items (e.g., email messages, meetings, and contacts) from Exchange Online and on-premises Exchange servers.

This API is used by various apps, including but not limited to Outlook desktop add-ins, older versions of Outlook for Windows, the Apple Mail / Calendar on macOS, and various other apps.

In February, the company announced it will start blocking the EWS API by default on October 1, 2026, but will let IT administrators temporarily maintain access via an app allowlist until the final shutdown on April 1, 2027. However, when EWS is disabled, the apps show errors ranging from alerts that the EWS protocol is unavailable to repeated prompts to enter the username or password.