code: @Override
      public String getMailURL(String CorpNum, MgtKeyType KeyType, String MgtKey) throws PopbillException {
          if (KeyType == null)
              throw new PopbillException(-99999999, "관리번호형태가 입력되지 않았습니다.");
          if (MgtKey == null || MgtKey.isEmpty())
              throw new PopbillException(-99999999, "관리번호가 입력되지 않았습니다.");
  
          return getMailURL(CorpNum, KeyType, MgtKey, null);
      }
docs: /*
  (non-Javadoc)
  @see com.popbill.api.TaxinvoiceService#getMailURL(java.lang.String, com.popbill.api.taxinvoice.MgtKeyType, java.lang.String)