Is it possible to automatically add a resource mailbox when a meeting invitation is sent to another resource mailbox?

Exchange Online.

I have a scenario where, when a user books a resource mailbox by adding it to a meeting invitation, I need to enforce booking another resource mailbox too; the underlying logic is something like "when you book this equipment, you must also book the room where it resides".

I'd like this to be automated, instead of requiring the users to add both resources to their meeting invitation.

How can this be implemented, if it can be implemented at all?

The resource mailboxes auto-accept meeting requests if they receive them.

Solution 1:

You could create a transport rule to add the another resource mailbox to the 'TO'box:

If you want the resource mailbox to accept meeting request automatically, you could run below command to configure it:

Set-CalendarProcessing -Identity "resource mailbox" -AutomateProcessing AutoAccept

For more details: Set-CalendarProcessing