Can I add or delete mailboxes myself?

While you can add and delete mailboxes through the control panel (mycpsrvr.com), you do not have the ability to increase/decrease the number of mailboxes because it's not tied to our billing system.

If you know that you're going to hire a new employee, please submit a support ticket in advance and we'll increase your mailbox limits so you can add their mailbox when they're hired.
 
Alternatively, you can buy a couple extra mailboxes for emergencies (yes, some customers actually do this).