You can modify the settings of your mailbox, such as enable email redirection, enable spam filtering, set out-of-office message or change the mailbox password. Login with the same username and password that you use when reading email.
You can create, remove and modify mailboxes and aliases. Login using the management account.
If DNS management (add-on) has been enabled for you, you can change the nameservice records of your domains yourself. Login using the management account.
If you have a MySQL database, you can manage it here.
If you have a PostgreSQL database, you can manage it here.