CbPlus is a licensed on a “per user” basis, so it means that the number of licenses must correspond, at leats, with the total number of mailboxes in your server.
Of course, you can always have addtitional licenses for an emergency or if you plan to increase the number of mailboxes in the short run.
System accounts (ham, spam, quarentyne, galsync, etc.) do not count for licensing purposes.
You can quote and purchase your license HERE.
If you have any doubt, you can contact our Sales Team.