Microsoft has set a clear end date for Exchange Web Services (EWS) within Microsoft 365 and Exchange Online.
Microsoft will disable Exchange Web Services by default in Microsoft 365 and Exchange Online starting October 1, 2026. Companies that still need EWS can temporarily keep the service active by setting the EWSEnabled flag to true before August 2026.
On the road to retirement for years
Exchange Web Services has been deprecated for a while. Microsoft announced the discontinuation in 2023, and in 2025, the company stopped providing access to certain licenses (such as F1 and F2). The API, which dates back to Exchange Server 2007, is widely used by integrations, third-party tools, and older applications such as classic Outlook. Attackers also find the API interesting. After the Midnight Blizzard incident, Microsoft indicated that it had accelerated the phase-out, writes The Register.
The decommissioning applies to Microsoft 365 and Exchange Online; nothing changes for on-premises Exchange Server. Microsoft recommends Microsoft Graph as a successor. Even Microsoft has not yet fully completed its own migration, writes The Register.
Scream tests
To detect hidden dependencies, Microsoft may conduct temporary scream tests in which EWS is briefly disabled and re-enabled. Administrators hoping for further postponement will not be heard: according to Microsoft, there will be no postponement after April 2027.