Free busy not working in an Exchange 2016 CU17 Hybrid environment.
When a customer forgets to tell you that they previously configured Exchange Hybrid using the Modern hybrid agent, The modern hybrid agent leaves behind some configuration settings that prevent free-busy working from EOL to EOP.
I always use the classic hybrid wizard for organisations that require long term rich co-existence.
The frustrating this with this issue is that the Exchange Remote Connectivity analyzer tests WORK, which would lead you to believe everything is ok and configured correctly. But when you attempt to query availability requests for a user or resource from OWA or Outlook , the look up fails.
What does the Hybrid Agent leave behind in Exchange Online?
Two values are populated that will prevent free \ busy from EOL to EOP working.
- OrganizationRelationship -targetsharingepr
- Intraorgconnector -targetsharingepr
When you query these values , You may see a value like https://a75aa21a-2f8d-4b2e-85fe-1234.resource.mailboxmigration.his.msappproxy.net/EWS/E
xchange.asmx
To resolve the issue run the following commands
- set-intraorgconnector -TargetSharingEpr $null
- set-OrganizationRelationship “Name of Org Relationship” -TargetSharingEpr $null
Microsoft Information Protection 
I was wondering about that entry and where it came from. Still not working but i didn’t like that entry anyhow.
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