Returns a Mailbox corresponding to an account. Usefull to get the
        size (attribute 's'), and the mailbox ID, returns nothing appart from
        that.

def get_account_mailbox(self, account_id):
        """ Returns a Mailbox corresponding to an account. Usefull to get the
        size (attribute 's'), and the mailbox ID, returns nothing appart from
        that.
        """
        selector = zobjects.Mailbox(id=account_id).to_selector()
        resp = self.request_single('GetMailbox', {'mbox': selector})

        return zobjects.Mailbox.from_dict(resp)