Microsoft To Shut Down Exchange Online EWS In April 2027

Microsoft has announced that Exchange Web Services (EWS) for Exchange Online will be fully shut down on April 1, 2027. The move marks the end of nearly two decades of EWS support in Microsoft’s cloud email ecosystem

Exchange Web Services is a cross-platform API introduced with Exchange Server 2007. It enables applications to access Exchange mailbox data, including emails, calendar events, meetings, contacts, and tasks. Over the years, EWS has been widely used by Microsoft’s own tools and countless third-party applications across both cloud and on-premises Exchange environments.

Why Microsoft Is Retiring EWS

According to Microsoft, EWS no longer meets today’s expectations around security, scalability, and reliability. Over the past several years, Microsoft has steadily shifted its own services and customers toward the Microsoft Graph API.

“EWS was built nearly 20 years ago, and while it served the ecosystem well, it no longer aligns with today’s security, scale, or reliability requirements,” the Exchange Team wrote in a blog post published on Thursday.

The Redmond giant added that Graph has reached near-complete feature parity for most EWS scenarios, and many third-party vendors have already completed or begun the transition.

“Retiring EWS lets us reduce legacy surface area, simplify platform behavior, and deliver a more consistent, modern experience for everyone,” it added.

A Phased Shutdown Starting In 2026

Rather than disabling EWS overnight, Microsoft is rolling out a phased retirement plan that will give administrators time to prepare.

Microsoft will manage the transition using a tenant setting called EWSEnabled, which can be set to True, False, or left as Null (the current default).

From October 1, 2026, EWS will be blocked by default in Exchange Online tenants. However, administrators who still rely on EWS can temporarily keep it enabled by configuring an application allow list and explicitly setting EWS permissions.

Tenants that do not take action will see EWS automatically blocked starting October 2026, although Microsoft plans to pre-populate allow lists in September 2026 based on actual usage to minimize service disruptions.

Further, organizations that proactively configure an allow list and set EWSEnabled to True by the end of August 2026 will avoid this automatic blocking.

The final and irreversible shutdown of EWS will take place on April 1, 2027, in Exchange Online, after which no exceptions will be granted. At that point, administrators will no longer be able to control or re-enable EWS in their tenants. Any applications that still depend on EWS will stop working in cloud mailboxes.

Impact On On-Premises And Hybrid Environments

The EWS shutdown applies only to Microsoft 365 and Exchange Online. Organizations running on-premises Exchange Server will still be able to use EWS.

Hybrid environments, however, will need careful planning. Microsoft clarified that on-premises mailboxes must move to Microsoft Graph, while on-premises mailboxes can continue using EWS. Autodiscover will help applications determine mailbox locations automatically, but hybrid customers will need Exchange Server Subscription Edition (Exchange SE) to support Graph access to Exchange Online.

What Organizations Should Do Now

Microsoft is urging administrators to begin preparing immediately by reviewing EWS usage reports in the Microsoft 365 admin center, identifying applications that still rely on EWS, and planning migrations to Microsoft Graph.

To help avoid surprises, Microsoft will send monthly Message Center notifications with tenant-specific usage summaries and reminders. The company may also conduct temporary “scream tests,” temporarily disabling EWS to help organizations uncover hidden dependencies.

The Bottom Line

With the countdown to April 2027 officially underway, Microsoft is making it clear that Exchange Online customers should not wait. Early planning and migration to Microsoft Graph will help ensure a smooth transition — and avoid last-minute disruptions when the legacy API reaches its final sunset in 2027.