code: def validate(self):
          
          missing = []
          for k, v in self._map.items():
              attr = getattr(self, k, False)
              if not attr or attr == CONFIG_PLACEHOLDER:
                  missing.append(v)
          if missing:
              return "Missing or invalid config values: {}".format(
                  ", ".join(sorted(missing))
              )
docs: Could this config be used to send a real email?