On-premise exchange users are unable to see the free/busy status of the exchange online users.

Question

We are sometimes having issues viewing Free/Busy information from on-prem mailboxes to Exchange Online mailboxes.

The opposite is also true, Exchange online mailboxes are having issues viewing on premise mailboxes Free/Busy information

When I say Free/Busy, I really mean appointment details. “Free”/”Busy”/”Tentative” seems to always be displayed, however we’re expecting to be able to see the actual meeting subject and maybe the body of the appointment depending on how permissions were delegated. This is not a problem for everyone. I have a few test mailboxes setup, and I can view their meeting details, and they can view mine.

Some of our employee/managers sometimes can see meeting details for another employee, and sometimes all they can see is Free/Busy information.

I have verified that if an on-premise user give an Exchange Online user “Limited Details” (View Free/Busy and meeting subject) permission, the Exchange online users will only be able to see Free/Busy and no subject. If the on-premise users gives and Exchange Online user “Reviewer” permission, they the Exchange Online user will be able to see Free/Busy, Subject, and Body details……..unless they’re having problems that day and can only see Free/Busy. Do the more granular permissions not work? Does an on-premise user need to grant at least Reviewer permission to an Exchange Online mailbox?

I’m assuming the problems with only seeing Free/Busy instead of full meeting details is because the reviewer is somehow not properly authenticated to Exchange Online (if mailbox is on-prem) or to On-prem (if mailbox is Exchange Online). If that is true, where in Outlook do I need to look to verify everyone is authenticated correctly?

Assuming we properly given permissions (such as Reviewer) access to a calendar, how can we troubleshoot?

How long does it take for permissions to go into effect or to be removed?

Answer 1

@SY_MSO

Based on your description, this phenomenon occurs sometimes, sometimes not. I think the configuration in your organization is correct, this phenomenon may related with network. It is suggested migrated mailboxes to Exchange online, Free/Busy will work better in the same side.

About this phenomenon, you could try to remove this exist permission, then give a higher level of permission, then check whether it could works better. You can also create a “Individual Sharing” in EAC under Organization. Then apply this new sharing policy to the mailbox that you want to shared calendar.

How long does it take for permissions to go into effect or to be removed?

For Exchange on-premises, it could works quickly. For Exchange online, there may exist some delay. At least they should take effect within 24 hours.

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