The space taken for mailboxes is part of the total disk space of the hosting account. The hosting plans offer different disk space.
SuperHosting.BG would not impose restrictions on the distribution of disk space in the hosting account. Mailboxes can use the whole disk space.
When creating an email account in cPanel you can determine if its quota is restricted to certain megabytes or unlimited - fill up the whole disk space in the hosting account.
How much disk space is occupied by an email account can be seen in cPanel -> (Email) Email Accounts.
