Exchange Hybrid free / busy not working after changing certificate

Question

Hello everyone,

I hope someone can help me with this one, because I have tried everything.

We have two Exchange Servers 2016 in DAG and a full Hybrid Setup for a while now.
Last week we switched out the main frontend certificate (not the Exchange Server auth certificate!) and since then the hybrid free/busy calendar access stopped working in both directions.
The users are getting a warning when opening the other calendar, that it couldn't be updated.
The remote connectivity analyzer is giving me the following error:

The mail recipient is not found in Active Directory., inner exception: Microsoft.Exchange.InfoWorker.Common.Availability.InvalidOrganizationRelationshipForRequestDispatcherException: The organization relationship O365 to On-premises - <...> can't be used. Please confirm that the organization relationship is configured correctly. . Name of the server where exception originated: BE0P281MB0196. LID: 52108

I already tried the following things:

• reran Exchange hcw multiple times. It completes successfully, but says it can't setup OAUTH
• checked OAUTH Setup. Successfully ran test-oauthconnectivity in both directions
• compared the organizationrelationship with other working setups
• checked if any certificates expired
• checked every article I found regarding hybrid free busy errors

I am not sure, whether the certificate is actually the reason, or just bad timing. Maybe somebody has an idea for me.

Thank you,
Patrick

Update: The on premise User can see the Online Calendar after enabling the IntraOrganizationConnector on the on permise Server. Apparently the hcw turns it off, because of the OAUTH Error.

Sadly, doing the same in Exchange Online didn't do anything. This was also disabled.

Answer 1

solved. Activating the IntraOrganizationConnector in EXO seems to be the fix.

Hi @Patrick ,

Great to know that the issue has already been resolved and thanks for sharing the solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to "Accept" the answer : )

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[Exchange Hybrid free / busy not working after changing certificate]

Issue Symptom:

"We have two Exchange Servers 2016 in DAG and a full Hybrid Setup for a while now.

Last week we switched out the main frontend certificate (not the Exchange Server auth certificate!) and since then the hybrid free/busy calendar access stopped working in both directions.

The users are getting a warning when opening the other calendar, that it couldn't be updated.

The remote connectivity analyzer is giving me the following error:

The mail recipient is not found in Active Directory., inner exception: Microsoft.Exchange.InfoWorker.Common.Availability.InvalidOrganizationRelationshipForRequestDispatcherException: The organization relationship O365 to On-premises - <...> can't be used. Please confirm that the organization relationship is configured correctly. . Name of the server where exception originated: BE0P281MB0196. LID: 52108"

Resolution:

Activating the IntraOrganizationConnector in EXO seems to be the fix.

Answer 2

solved. Activating the IntraOrganizationConnector in EXO seems to be the fix.