Migrate Free/Busy, MailTips, and Calendar Sharing before EWS deprecation

Exchange Web Services (EWS) deprecation starts October 1, 2026, affecting cross-tenant Free/Busy, MailTips, and Calendar Sharing. Migrate to Microsoft 365 Cross-Tenant Access Policy by September 2026 to avoid disruption. Rollout begins August 2026 worldwide; check tenant settings and follow migration guidance. What and Why: Exchange Web Services (EWS)deprecation begins October 1, 2026. Cross-tenant collaboration features— Free/Busy, MailTips, and Calendar Sharing — currently rely on EWS. Cross-tenant Free/Busy,MailTips, and Calendar Sharing via Microsoft 365 Cross-Tenant Access Policy,which replaces EWS-based cross-tenant collaboration, will be available starting September 2026. Rollout Schedule: Worldwide: We will begin rolling out in August 2026 and expect to complete by September 1, 2026. GCC: We will begin rolling out mid-August 2026 and expect to complete by mid-September 2026. GCC High: We will begin rolling out early September 2026 and expect to complete by end of September 2026. DoD: We will begin rolling out early September 2026 and expect to complete by end of September 2026. Impact on your organization: Sharing Free/Busy, Calendars,and MailTips (e.g., out of office message) with another Microsoft 365organization via Organization Relationship, Availability Address Space, orSharing Policy relies on Exchange Web Services (EWS), which is beingdeprecated. To preserve these cross-tenant collaboration scenarios, you willneed to start migrating to Microsoft 365 Cross Tenant Access Policy. Your tenant is affected if it usesany of the following Exchange Online configurations: Organization Relationships — sharing Free/Busyor MailTips with other Microsoft 365 tenants  Availability Address Spaces — sharing Free/Busy withother Microsoft 365 tenants (AccessMethod: OrgWideFBToken)  Sharing Policies — sharing calendarsexternally, either via invitations sent to recipients in other Microsoft 365organizations or calendars published for anonymous access via an internet URL Run these commands in Exchange OnlinePowerShell to check if your tenant is affected:  Get-OrganizationRelationship| Format-List Name, DomainNames, Enabled, FreeBusyAccessEnabled,FreeBusyAccessLevel, FreeBusyAccessScope, MailTipsAccessEnabled,MailTipsAccessLevel, MailTipsAccessScope If results show(1) Enabled: True, and (2) either FreeBusyAccessEnabled: True orMailtipsAccessEnabled: True, and (3) the external organization is hosted inMicrosoft 365, your tenant is affected and in scope to migrate. Else, no actionis needed.  Get-AvailabilityAddressSpace| Format-List ForestName, AccessMethod  If results show(1) AccessMethod: OrgWideFBToken, and (2) the external organization is hostedin Microsoft 365, your tenant is affected and in […]

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