PHPMailer 中的 SMTP 连接()失败错误

I am completely new to PHP and I want to send a mail using PHP. I have a Contact Us form whcih will accept email is of the person contacting me and therefore the mail will be sent to me. I am using PHPMailer library from https://github.com/PHPMailer/PHPMailer/tree/master and following is the code snippet I am using.

<?php
require("class.phpmailer.php");
$mail = new PHPMailer();
$mail->IsSMTP();  

$mail->SMTPSecure = 'tls';

$mail->Host     = "resolver1.opendns.com"; // this SMTP server of my machine
//$mail->Host     = "208.67.222.222";//ip ; which one to use the resolver1.opendns.com or 208.67.222.222 ???

$mail->From     = "xyz@gamil.com;//email id of the person 

$mail->AddAddress("datta.dhonde@coreathena.com");//my email id

$mail->Subject  = "First PHPMailer Message";
$mail->Body     = "Hi! 

 This is my first e-mail sent through PHPMailer.";
$mail->WordWrap = 50;

if(!$mail->Send()) 
{
  echo 'Message was not sent.';
  echo 'Mailer error: ' . $mail->ErrorInfo;
}  
else 
{
  echo 'Message has been sent.';
}
?> 

我收到错误消息未发送.邮件程序错误:SMTP 连接()失败."我没有得到什么问题..?$邮件->主机="；请评论这代表什么?