Microsoft’s phased disablement of Exchange Web Services (EWS) in Exchange Online is reported to begin October 1, 2026. Apple Mail on Mac could lose access when a tenant blocks EWS if the account still relies on it and access has not been retained. Microsoft’s rollout is tenant by tenant, so the timing can differ between organizations.

Why Apple Mail on Mac could lose sync

EWS is an interface that apps use to connect with Exchange. Apple says Mail and Calendar on macOS use EWS for Exchange accounts. If an organization’s Exchange Online tenant disables EWS, an account that still depends on it may stop syncing.

Apple says it is working with Microsoft to add Microsoft Graph support to five Mac apps—Mail, Calendar, Contacts, Notes, and Reminders—in a future macOS 27 update. Graph is Microsoft’s API platform for connecting apps and services; Microsoft identifies it as the migration target for most EWS integrations and says some feature gaps remain.

How Microsoft’s tenant-level controls work

Microsoft uses the organization-level EWSEnabled setting to phase out EWS. As rollout reaches a tenant where the setting remains Null, Microsoft says it changes that value to False.

After enforcement, setting EWSEnabled=True does not by itself allow every app to use EWS. With an empty or unset EWS AppID Allow List, ordinary application traffic is blocked. A populated list permits the listed app IDs under Microsoft’s rules, which include an exception for specified cross-tenant organization-relationship traffic.

Microsoft says it will populate allow lists for tenants that have not created one, using each tenant’s usage. Administrators remain responsible for reviewing and managing the list. During the transition, an administrator can temporarily re-enable EWS by setting EWSEnabled=True; setting it to Null also re-enables EWS without restrictions. Microsoft warns that restoring access after a block can involve a service interruption. These settings do not extend service beyond the final shutdown.

Which Exchange accounts and devices are in scope

The retirement applies to EWS in Exchange Online, not to the Exchange Online service itself. Microsoft says EWS on on-premises Exchange Server is outside this retirement; in hybrid setups, scope depends on whether an app connects to a cloud or on-premises mailbox.

Apple documents a different Exchange connection method for iPhone and iPad: Exchange ActiveSync (EAS). The EWS retirement concerns the Mac EWS connection, not that mobile protocol.

Microsoft’s scheduled final shutdown

Microsoft has scheduled the permanent shutdown of EWS in Exchange Online for April 1, 2027.