PHPMailer无法连接到SMTP主机

SMTP -> ERROR: Failed to connect to server: php_network_getaddresses: getaddrinfo failed: No such host is known. (0)
SMTP Error: Could not connect to SMTP host. There was a problem sending this mail!

这是我的配置文件设置,因为我遵循了这个PHPMailer tutorial

// Configuration settings for My Site

// Email Settings
$site['from_name'] = 'Manish Dekavadiya'; // from email name
$site['from_email'] = 'manish@<my-domain>.com'; // from email address

// Just in case we need to relay to a different server,// provide an option to use external mail server.
$site['smtp_mode'] = 'enabled'; // enabled or disabled
$site['smtp_host'] = "smtp.<my-domain>.com";
$site['smtp_port'] = 587;
$site['smtp_username'] = "manish@<my-domain>.com";
$site['smtp_password']="<password>";

并使用了mailer类和教程中提到的扩展类如下：

/*****sendmail.php****/

// Grab our config settings
require_once($_SERVER['DOCUMENT_ROOT'].'/config.php');

// Grab the FreakMailer class
//echo $_SERVER['DOCUMENT_ROOT'];
require_once($_SERVER['DOCUMENT_ROOT'].'/lib/MailClass.inc');

// instantiate the class
$mailer = new FreakMailer();

// Set the subject
$mailer->Subject = 'This is a test';
 $mailer->SMTPDebug = 1;
// Body
$mailer->Body = 'This is a test of my mail system!';

// Add an address to send to.
$mailer->AddAddress('manish.dekavadiya@gmail.com','Manish Dekavadiya');

if(!$mailer->Send())
{
    echo 'There was a problem sending this mail!';
}
else
{
    echo 'Mail sent!';
}
$mailer->ClearAddresses();
$mailer->ClearAttachments();

当我尝试在phpmailer docs @ examples / test_smtp_gmail_basic.php中给出的示例时,还会出现另一个错误

SMTP -> ERROR: Failed to connect toserver: php_network_getaddresses:
getaddrinfo failed: No such host is
known. (0) SMTP Error: Could not
connect to SMTP host. There was a
problem sending this mail!

所以必须有设置或配置错误.没有代码错误.