Microsoft has confirmed that the Exchange Web Services (EWS) API for Exchange Online will be permanently shut down in April 2027, bringing an end to a technology that has been in use for nearly two decades.
Exchange Web Services, commonly known as EWS, is a cross-platform API that allows applications to access Exchange mailbox data such as emails, calendars, contacts, and tasks. It has supported both cloud-based Exchange Online and on-premises Exchange Server installations since Exchange Server 2007.
Microsoft said it will start blocking EWS access in Exchange Online by default on October 1, 2026. Administrators will still be able to keep EWS running temporarily by using an application allowlist, but the final shutdown will take place on April 1, 2027, with no extensions or exceptions.
Organizations that configure allowlists and required settings by the end of August 2026 will avoid the automatic blocking in October. For tenants that do not take action, Microsoft will automatically generate allowlists starting in September 2026 based on observed EWS usage. The company also plans to run temporary “scream tests,” which briefly disable EWS to uncover hidden dependencies before the final cutoff. IT administrators will receive regular updates through the Microsoft 365 Message Center, including tenant-specific usage details and reminders.
Microsoft emphasized that this retirement affects only Exchange Online and Microsoft 365. On-premises Exchange Server environments will continue to support EWS, meaning organizations running local mail servers can still rely on the API for now.
In its announcement, the Exchange Team said EWS no longer meets modern security, scalability, and reliability standards. As a replacement, Microsoft is urging developers to migrate to the Microsoft Graph API, which now offers near-complete feature parity with EWS for most use cases.
For hybrid environments, Microsoft clarified that on-premises mailboxes can continue using EWS, but cloud mailboxes must move to Microsoft Graph. Autodiscover will help applications detect where mailboxes are hosted. However, only Exchange SE will support Graph access to Exchange Online, meaning hybrid customers will need Exchange SE to host on-premises mailboxes.
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This announcement follows Microsoft’s earlier warnings. In 2018, the company said EWS would stop receiving new features, and in October 2021, it deprecated 25 rarely used EWS APIs, fully removing them in March 2022 for security reasons. Microsoft first confirmed plans for the full EWS retirement in September 2023.
