Determine which mailboxes are considered for Licensing

Question / Problem

How can I see which mailboxes the "Exchange Server Toolbox" recognizes for licensing/are licensed.

Answer / Solution

The "Exchange Server Toolbox" by default uses all user mailboxes on the exchange server, excluding room and device mailboxes.
In the configuration interface under "Licensing", you can see which and how many mailboxes the "Exchange Server Toolbox" uses for licensing.

There you can also exclude individual mailboxes from processing and thus from licensing.