When you use Hybrid Setup Wizard to configure federation in an Exchange Server 2010 SP2-based hybrid environment, the wizard could not complete and you receive the following error message:
Unable to reserve domain "FYDIBOHF25SPDLT.exchangedelegation.<your domain>" for Application Identifier "<XXXX>". Detailed information: " Windows Live returned a domain reservation error. Detailed information: "DomainUnavailable: The specified domain is not available.".
Exchange Management Shell command attempted:
Set-FederatedOrganizationIdentifier -DelegationFederationTrust 'Microsoft Federation Gateway' -AccountNamespace 'exchangedelegation.<your domain>' -OrganizationContact '' -Enabled $true
Therefore, on-premises users cannot view free/busy information of cloud users, and vice versa.
The issue occurs because the exchangedelegation domain is incorrectly added when creating federation trust in Exchange Server 2010 SP2-based hybrid environment. The incorrect Federation Trust and Organization Relationship prevent free/busy information from sharing.
To resolve the issue, manually correct the Federation Trust and Organization Relationship settings by running the following cmdlet to add the Primary SMTP Domain:
Set-FederatedOrganizationIdentifier -DelegationFederationTrust 'Microsoft Federation Gateway' -AccountNamespace '<your domain>' -Enabled $true
Exchange Hybrid Deployment Configuration Tips: Sharing Free/Busy Information
Create a Federation Trust
Exchange hybrid configuration