Free-busy sharing across two M365 tenants (full cloud) doesn't work

Iron Contributor

I was hoping the Organization Sharing would allow two Exchange Online Tenancies (full cloud) to share calendar availabilities across. i.e. If user 1 in Tenant A trying to schedule a meeting with user 2 from Tenant B, user 1 in Tenant A should be able to see the availability of user 2 upfront in the scheduling window (just like how the availability works internally). 


I've created the relationship from Organization sharing (see below) using Microsoft's official guidance. 


Ref: Create an organization relationship in Exchange Online | Microsoft Learn

Command used:


New-OrganizationRelationship -Name "Contoso" -DomainNames "","","" -FreeBusyAccessEnabled $true -FreeBusyAccessLevel LimitedDetails




This was done from both tenancies but the availability deosn't seem to work (see below. Greyed out question marks are the users from tenant B as user 1 from Tenant A tries to schedule a Outlook meeting). 




Has anyone implemented this ? am I missing anything here?


any inputs are highly appreciated ! 


Thank you


3 Replies
Apart from creating org relationships, make sure that the individual permission levels on user's calendar allow for the Default user to see the appropriate details. You can also go over the troubleshooting steps here:
While some of them apply only to Hybrid scenarios, most can be used for generic free/busy troubleshooting.

Thanks for your swift response. Default permissions are on.

FolderName User AccessRights
Calendar Default {AvailabilityOnly}
Calendar Anonymous {None}

Back to basics, I'm wondering if cross-tenant free-busy sharing is even supported because none of the official documentation specify that point.
It's supported, at least for the global "multi-tenant" instance of Exchange Online.