public function postAddMail(Request $request)
 {
     $validate = Validator::make($request->all(), ['memberId' => 'required', 'address' => 'required|email']);
     if ($validate->fails()) {
         $e = new InvalidArgumentHttpException();
         $e->setMessage('잘못된 요청입니다.');
         throw $e;
     }
     $address = $request->get('address');
     if ($this->handler->findMailByAddress($address)) {
         throw new MailAlreadyExistsException();
     }
     $mail = new MailEntity($request->only('address', 'memberId'));
     $mail = $this->handler->insertMail($mail);
     return Presenter::makeApi(['mail' => $mail]);
 }