ESP8266 first code help

Projects General Guidance
29 
    client.println("POST /pushingbox HTTP/1.1");
    client.println("Host: api.pushingbox.com");
    client.println("Connection: close");
    client.println("Content-Type: application/x-www-form-urlencoded");
    client.print("Content-Length: ");
    client.println(postStr.length());
    client.println();
    client.println();
    client.print(postStr);

\n\n is not \r\n\r\n