Limit mailbox size and mail domain size in cPanel
There should be an option to set maximum size of the mailboxes created in the server and the domain as a whole. The limit should be applied to all users by default and the cpanel user should not be able to assign quota more than the maximum mailbox size limit. For example, the cpanel account can create user with 500 MB but cannot create an user with more than 1 GB if the default size limit is set to 1 GB. Similarly, we set a quota for the mail domain say 5 GB. This should ensure that the domain should not exceed 5 GB irrespective of the actual usage of the individual mailboxes.