如何使用php-ccurl发送SMTP请求和读取响应

我正在尝试将smtp请求发送到安装在freebsd中的smtp服务器，并读取成功或失败响应？这是我的代码：

$url = '192.168.1.227:25/';
    $user = 'admin';
    $pass = '123';
    $params = array(
        'User'      => $user,
        'passwor'   => $pass,
        'to'        => 'example1@example.com',
        'subject'   => 'test',
        'html'      => 'body',
        'text'      => 'text',
        'from'      => 'example2@example.com',
      );

    $session = curl_init($url);
    curl_setopt ($session, CURLOPT_POST, true);
    curl_setopt ($session, CURLOPT_POSTFIELDS, $params);
    curl_setopt($session, CURLOPT_HEADER, 1);
    curl_setopt($session, CURLOPT_RETURNTRANSFER, true);
    $response = curl_exec($session);
    $info = curl_getinfo($session);
    curl_close($session);
    echo $response;
    print_r($info);