Exchange server Plus CALs

Hi Guys,

I would like to have better understanding about CALs, for example: in an Exchange server (on-premise) environment, with 40 users mailboxes operating at the time, but but the Exchange server CALs covers only 5 user mailboxes.

What are the pros and cons, the issues to be encountered, etc.

Some of the clients are care about getting the remaining user/device CALs simply because is still working for them.

Thanks.

yours affectionate Niyi Okunola