Hybrid Exchange - Migrated users unable to see on-prem room mailboxes/other shared mailboxes

Joe Grover 156 Reputation points

Last week I completed a Hybrid Configuration setup between our on-prem Exchange 2016 servers and 365. I've migrated myself and a couple of other IT staff.

I did a Full Hybrid Configuration using the Classic Hybrid Topology.

So far everything appears to be working normally, however I no longer have access to any of the conference room calendars or mailboxes I had full access to pre-migration (all of which are still on-premises). Clicking on a conference room calendar in my Shared Calendars doesn't bring up anything at all (not even a blank calendar, it's like it doesn't even register that I clicked on it). I can click on on-prem calendars from user mailboxes and see their free/busy data, but not the room mailboxes.

I found an article indicating that the default permission on these calendars is None and that I should change that to Free/Busy or one of its variants, but looking at the affected calendars they're already set to Reviewer (Full Details) so that isn't the issue.

I looked at Organization - Sharing in the 365 EAC and it shows that sharing is enabled on the migration endpoint:


Please advise.

Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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Accepted answer
  1. Andy David - MVP 142.7K Reputation points MVP

    Are you sure those room objects are actually synced to 365?

    get-recipient <room>

    Do you see it via Exchange Online Powershell?

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