After nearly two decades of service, Microsoft will be phasing out Exchange Web Services (EWS) for Microsoft 365 and Exchange Online. The tech giant will disable EWS by default for Exchange Online tenants by October 2026, with the final shutdown being set for April 1, 2027.
Microsoft stressed that the change only applies to M365 and Exchange Online cloud environments, but that EWS will continue to work for on-prem Exchange Servers. Explaining the move, the company said that since EWS was built nearly 20 years ago, it no longer meets modern security, scale and reliability needs. By retiring Exchange Web Services, the tech titan can reduce the legacy attack surface, apart from simplifying platform behaviour, and most importantly, delivering a more consistent, modern experience.
“If you proactively configure an Allow List and set EWSEnabled to True by the end of August 2026, your tenant will be excluded from the October 1 automatic change to EWSEnabled=False,” Microsoft shared in a post explaining the disabling process for EWS.
Microsoft’s own applications have already largely migrated from EWS or are nearing completion. Third-party apps, too, have either made the switch or are actively working on the transition. System admins can also re-enable EWS after it’s blocked by default after the October 2026 milestone, though temporarily, as the April 2027 shutdown remains firm and non-negotiable.
“Microsoft is disabling EWS per tenant via the EWSEnabled property, which supports three values: True, False, and Null (currently the default). In early 2026, a new feature will be introduced that allows administrators to define an AppID Allow List. When enabled, only apps on that list will have access to EWS,” reported Techzine on the process, while adding, “As of October 1, 2026, the EWSEnabled value for tenants that still have it set to Null will automatically change to False. This means that EWS will be blocked for all applications in that tenant. Organisations that still need EWS will have two options: set EWSEnabled to True and maintain an Allow List, or set EWSEnabled back to Null to continue using EWS without restrictions until its final discontinuation. Administrators who proactively configure an Allow List and set EWSEnabled to True before the end of August 2026 will be excluded from the automatic change on October 1. Microsoft will pre-populate the Allow List for customers who have not created one before September 2026, based on actual usage per tenant.”
While Microsoft has promised to send system admins monthly “Message Centre” posts with summaries and reminders regarding EWS phase-out, some disruptions may come from the tech giant’s “scream tests,” designed to temporarily shut down EWS services to highlight any dependencies ahead of the major milestones.