It’s for real this time: After nearly 20 years, there will soon be no more Exchange Web Services (EWS) in Microsoft Exchange Online.

The API will be disabled by default on October 1, 2026, and will be completely shut down on April 1, 2027, with “no exceptions.” Organizations must have switched to Microsoft Graph by then. However, admins can give themselves a little more wiggle room if they change a configure setting and create allow lists in EWS — but they must do so by the end of August 2026, or they’ll lose access to EWS on the cutoff date.

It’s important to note that this retirement process only applies to Microsoft 365 and Exchange Online. EWS will continue to function as usual in on-premises Exchange Server environments.

“Microsoft wants everyone to use Graph, which is better for them, and theoretically for you,” said Jeremy Roberts, senior director for research and content at Info-Tech Research Group.

EWS “has been on the chopping block for ages,” he noted. “They announced that it would get no feature updates in 2018, so the writing really should have been on the wall a long time ago.”

A phased disablement plan

EWS is a legacy cross-platform API for app development that provides access to mailbox items such as email addresses, contacts, and calendars in Exchange Online and post-2007 on-premises versions of Exchange Server. It’s popular with system integrators connecting to in-house apps like Outlook, as well as with third parties.

The API has been deprecated for nearly a decade and has received no functionality updates for eight years. Microsoft announced its retirement in 2023, warning that it would be fully disabled in Exchange Online in October 2026. It further confirmed in 2025 that Microsoft 365 and Office 365 F1 and F2 license types would be prevented from using EWS beginning March 1, 2026.

The tech giant calls this final retirement process a “phased, admin controllable disablement plan.”

“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,” Microsoft notes.

In its stead, users must switch to Microsoft Graph, an API platform that allows developers to integrate with critical Microsoft products like Microsoft 365, Windows, and Azure. It also supports connectivity between Windows and other platforms like iOS and Android. Graph was released in November 2015 as Office 365 Unified API.

Microsoft says Graph has reached “near-complete feature parity” for the “vast majority” of EWS use cases. The company’s own apps have been migrated to the API or are “nearing completion,” and many third-party vendors have made the switch or are “actively doing so.”

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

To “focus minds” on EWS’ retirement, the company may perform “temporary scream tests,” a late-stage decommissioning technique where systems are briefly turned off to “expose hidden dependencies” and see if any users report issues or make complaints.

The company says it will also keep admins informed via Message Center notifications on a monthly basis, providing “tenant-specific” reminders and usage summaries.

Still using EWS in Microsoft Exchange? Take action now

So what should admins do now? “Ideally, nothing,” said Info-Tech’s Roberts, as they should have already moved over to Graph.

However, those who use third-party services or have built in-house email integrations that rely on EWS will have to migrate, he noted, adding, “you could experience some disruption.”

This is a good reminder that cloud services are managed at scale for the benefit of the provider, Roberts said, and this is part of Microsoft’s push to eliminate technical debt. “In this case, eight years is a long time,” he said. “Sysadmins should pay attention, understand where vendors are going, and mitigate with proactive updates.”

Microsoft’s plan is to disable EWS tenant-by-tenant using the EWSEnabled property, a setting in Exchange Online that essentially works as an on-off switch to control access to EWS. The property supports three values: “true” (access allowed), “false” (access denied), and “null” (the default setting today). On October 1, 2026, null values will automatically change to false, meaning EWS will be blocked for all apps.

“If you want to keep EWS blocked, you can simply leave it that way,” Microsoft explains.

However, those still requiring access to EWS can re-enable the service by setting EWSEnabled to “true” and creating AppID allow lists, a new feature set to arrive in “early 2026” that will only allow specified apps to access EWS. These tasks must be completed by the end of August 2026 if the tenant wishes to be excluded from the automatic October 1 EWS block.

Beginning in September, Microsoft says it will pre-populate allow lists for customers who have not created their own, based on each tenant’s usage patterns. On October 1, if EWSEnabled has not been set to “true,” EWS will be blocked for all apps.

Admins will still be able to toggle EWSEnabled  to “true” at this point, “but note that there will be a service interruption in this case,” Microsoft warns.

Alternatively, customers can toggle EWSEnabled back to null via Exchange Online PowerShell. Allow lists will essentially be ignored with this setting, and there will be no EWS restrictions until the final deprecation in 2027. Then, regardless of the setting, EWS will cease to function.

This is really the end, Microsoft emphasizes. Customers are advised to evaluate their environment, talk with application owners, and plan their move to Microsoft Graph. “Early action avoids last‑minute surprises and gives you the smoothest possible transition path,” the company says.