An Exchange Server 2003 user cannot view the free/busy information of Office 365 resources or users within a Hybrid deployment.
In an Exchange 2003 and Office 365 Hybrid Deployment environment, the Office 365 users are able to view the Free/Busy information of Exchange 2003 users or resources. However, the Exchange 2003 user may not be able to view the Free/Busy information of the Office 365 users or resources unexpectedly.
Many configuration issues may result in the issue mentioned in the symptoms. Below two issues are observed in the business environment:
The primary proxy address may not be configured correctly.
How to identify this issue
From the network trace, you will see the following information when the Exchange 2003 users queries Free/Busy information of the Office 365 users or resources:
ADProvider FederatedIdentity Could not find a SMTP proxy address corresponding to a federated accepted domain for user <domain>/Users/FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042
How solve this issue
Use the Set-Mailbox cmdlet to correct the primary SMTP proxy. A sample is listed below:
Set-Mailbox -Identity FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042 -Arbitration -EmailAddresses FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042@<domain>
More information about the Set-Mailbox cmdlet
The permission for the related Free/Busy folder may not be configured correctly. For example the permission for External (FYDIBOHF25SPDLT) Free & Busy folder is incorrect
Default permission: Author
Default permission: Editor
Exchange Server 2003
Exchange Server 2010
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