def mailbox(self, resource=None):
return MailBox(parent=self, main_resource=resource, name='<STR_LIT>')<EOL>
Get an instance to the mailbox for the specified account resource

        :param str resource: Custom resource to be used in this mailbox
         (Defaults to parent main_resource)
        :return: a representation of account mailbox
        :rtype: MailBox