code: private void notifyStatus(SmsMessage message) {
          URI callback = message.getStatusCallback();
          if (callback != null) {
              String method = message.getStatusCallbackMethod();
              if (method != null && !method.isEmpty()) {
  
                  if (!org.apache.http.client.methods.HttpGet.METHOD_NAME.equalsIgnoreCase(method)
                          && !org.apache.http.client.methods.HttpPost.METHOD_NAME.equalsIgnoreCase(method)) {
                      final Notification notification = notification(WARNING_NOTIFICATION, 14104, method
                              + " is not a valid HTTP method for <Sms>");
                      storage.getNotificationsDao().addNotification(notification);
                      method = org.apache.http.client.methods.HttpPost.METHOD_NAME;
                  }
              } else {
                  method = org.apache.http.client.methods.HttpPost.METHOD_NAME;
              }
  
  
              List<NameValuePair> parameters = populateReqParams(message);
              HttpRequestDescriptor request = new HttpRequestDescriptor(callback, method, parameters);
              downloader().tell(request, self());
  
          }
      }
docs: The storage engine.