code: public void sendAll(String apiKey, String queue, Collection<?> messages) {
          checkNotNull(queue, "queue");
          checkNotNull(messages, "messages");
          if (messages.isEmpty()) {
              return;
          }
          try {
              URI uri = _queueService.clone()
                      .segment(queue, "sendbatch")
                      .build();
              _client.resource(uri)
                      .type(MediaType.APPLICATION_JSON_TYPE)
                      .header(ApiKeyRequest.AUTHENTICATION_HEADER, apiKey)
                      .post(messages);
          } catch (EmoClientException e) {
              throw convertException(e);
          }
      }
docs: Any server can handle sending messages, no need for @PartitionKey