Microsoft has laid out a timeline for the disablement and shutdown of Exchange Web Services (EWS) in Microsoft 365 and Exchange Online.
October 1, 2026, is when EWS will be disabled by default, although tenants can keep the lights on a little longer by setting the EWSEnabled flag to true by August, but the service will be shut down entirely on April 1, 2027.
EWS has long been deprecated, and Microsoft announced its retirement in 2023. The noose tightened in 2025, with confirmation that certain license types (F1 or F2) would be blocked from using it.
The service is an API that allows applications to access mailboxes and data stores in Exchange Online and Exchange Server. It dates back to Exchange Server 2007, and has proven popular with integrators and third parties (as well as in-house applications such as Outlook Classic). It is also popular with miscreants. Following the Midnight Blizzard security incident, Microsoft "elevated the urgency" of pushing the tech out to pasture.
The retirement only applies to Microsoft 365 and Exchange Online. Nothing will change regarding EWS in Exchange Server.
The timeline means affected administrators who have not yet begun or completed a migration will need to get moving. Microsoft's preference is a move to Microsoft Graph. However, it noted the service is just at "near-complete" feature parity and even Microsoft itself had yet to conclude the migration of all its impacted applications.
To focus minds, Microsoft also said it "may perform temporary 'scream tests'" where it turns EWS off and on to expose hidden dependencies. It did not disclose how an administrator would differentiate a "scream test" from one of the depressingly regular outages that plague its online services. Was it deliberate, or did someone screw up a configuration file again?
Microsoft said: "We will provide more information in the coming weeks."
For administrators hoping Microsoft might blink and allow the service to run past the termination date, it said: "There will be no exceptions past April 2027." ®
Source: The register