Apple Mail and other built-in Mac apps may stop syncing Microsoft 365 work accounts as Microsoft begins disabling Exchange Web Services (EWS) by default in Exchange Online. The change affects the older protocol that Apple’s Mail and Calendar apps still use to connect to Microsoft-hosted business accounts.

Microsoft announced the first phase of the change on October 1, 2026. The rollout is phased, meaning affected organizations may not lose access at the same time. Companies that have elected to keep EWS enabled are not affected for now.

Why Microsoft 365 syncing may stop working

Microsoft stopped adding new features to EWS in 2018 and announced in 2023 that it would begin retiring the protocol in Exchange Online from October 2026. The company is replacing EWS with the newer Microsoft Graph API, which provides access to Microsoft 365 services.

For Mac users, the transition matters because Apple’s Mail, Calendar, Contacts, Notes, and Reminders apps have not yet moved to Graph support. Once EWS access is disabled for an organization, those apps may no longer be able to synchronize Microsoft 365 data.

The change applies only to Exchange Online, Microsoft’s cloud-hosted email service. Businesses operating their own on-premises Exchange servers are not affected by this particular retirement. iPhone and iPad users are also unaffected because Apple’s mobile operating systems use Exchange ActiveSync rather than EWS.

Apple is working on a macOS update

Apple acknowledges the compatibility issue in its platform deployment documentation. The company says it is working with Microsoft to transition the Mac versions of Mail, Calendar, Contacts, Notes, and Reminders to Microsoft Graph in a future macOS 27 update.

That update is not available yet. Apple skipped macOS 27.1 beta releases, and the release notes for current macOS 27.2 betas do not mention Graph support. As a result, some organizations may need an interim solution if their EWS access is removed before Apple completes the transition.

What affected organizations can do

IT administrators can currently restore access by keeping EWS enabled for their organization. Microsoft’s retirement process allows this option during the phased rollout, although it is not a permanent workaround.

Microsoft plans to shut down EWS in Exchange Online permanently on April 1, 2027, and says no extensions are currently planned. Organizations that cannot continue using EWS can move Mac users to a client compatible with Microsoft Graph, including Microsoft’s Outlook app.

The immediate impact will therefore vary by company. Administrators should check their Exchange Online settings and determine whether Apple’s native Mac apps will remain usable during the transition, while planning a move to Graph-compatible software before the final retirement date.