Free/Busy sharing moves to Cross-Tenant Access Policy
- Maxime Hiez
- Exchange
- 19 Aug, 2026
Introduction
The Exchange Online team announced the move of cross-tenant sharing of Free/Busy, MailTips and calendars to the Microsoft 365 Cross-Tenant Access Policy. These three scenarios rely today on Exchange Web Services (EWS), whose progressive disablement starts on October 1, 2026.
The change only concerns organizations that actually share this information with another Microsoft 365 tenant. Internal sharing, sharing in a hybrid environment and sharing with a fully on-prem Exchange organization are not affected.
The configurations concerned
Three Exchange Online objects are replaced :
- Organization Relationship : Sharing of Free/Busy and MailTips
- Availability Address Space : Sharing of Free/Busy, only when AccessMethod is set to OrgWideFBToken
- Sharing Policy : Sharing of calendars
Cross-Tenant Access Policy is an inbound setting. Each organization controls what external users can access on its side, which means that both tenants must create complementary policies for bidirectional sharing. Identification is done by Tenant ID and no longer by domain name, all the domains of the partner tenant being covered automatically.
Check if you are concerned
Three commands are enough to make the inventory from Exchange Online PowerShell :
Get-OrganizationRelationship | Format-List Name, DomainNames, Enabled, FreeBusyAccessEnabled, FreeBusyAccessLevel, FreeBusyAccessScope, MailTipsAccessEnabled, MailTipsAccessLevel, MailTipsAccessScope
Get-AvailabilityAddressSpace | Format-List ForestName, AccessMethod
Get-SharingPolicy | Format-List Name, Domains, Enabled, Default
You are concerned if an organization relationship comes back with Enabled set to True and FreeBusyAccessEnabled or MailTipsAccessEnabled set to True, if an Availability Address Space uses OrgWideFBToken, or if an active Sharing Policy carries a CalendarSharingFreeBusySimple, CalendarSharingFreeBusyDetail or CalendarSharingFreeBusyReviewer level towards a domain hosted in Microsoft 365.
What replaces what
The migration goes through the Microsoft Graph PowerShell SDK Beta module and through the activation of the Microsoft 365 Collaboration trust level in the Entra Cross-Tenant Access Policy. Each old configuration has its equivalent :
| Old configuration | New capability |
|---|---|
| FreeBusyAccessLevel AvailabilityOnly | crossTenantCalendarAvailabilityBasic |
| FreeBusyAccessLevel LimitedDetails | crossTenantCalendarAvailabilityLimitedDetails |
| MailTipsAccessLevel Limited | crossTenantMailTipsLimited |
| MailTipsAccessLevel All | crossTenantMailTipsAll |
| CalendarSharingFreeBusySimple | crossTenantCalendarSharingFreeBusySimple |
| CalendarSharingFreeBusyDetail | crossTenantCalendarSharingFreeBusyDetail |
| CalendarSharingFreeBusyReviewer | crossTenantCalendarSharingFreeBusyReviewer |
The old configurations take precedence over the new policies. They must therefore be disabled before validating the behavior, in coordination with the administrator of the partner tenant, then removed once the tests are conclusive.
The schedule to respect
The rollout of the feature spreads out depending on the environment :
- Worldwide : Rollout started in August 2026, completion expected on September 1, 2026.
- GCC : Start in mid-August, completion in mid-September 2026.
- GCC High and DoD : Start in early September, completion at the end of September 2026.
From October 1, 2026, the disablement of EWS progressively reaches the tenants and the sharing that depends on it stops working. Users in the partner tenant no longer see Free/Busy, MailTips or shared calendars, and the other way around.
note
Conclusion
The switch is mechanical but it requires coordination with each partner tenant, which takes time when the relationships are numerous. The inventory in three commands takes a few minutes and immediately tells you whether the topic concerns you. For the organizations concerned, the comfortable window closes on October 1, 2026, the EWSEnabled safety valve only postponing the deadline to April 1, 2027.
Sources
Microsoft Learn - Migrate to Microsoft 365 Cross-Tenant Access Policy
Microsoft Learn - Deprecation of EWS in Exchange Online
Did you enjoy this post ? If you have any questions, comments or suggestions, please feel free to send me a message from the contact form.
Don’t forget to follow us and share this post.
