PHPMailer error Couldnotinstantiatemailfunction

PHPMailer reports the error "Couldnotinstantiatemailfunction". I downloaded the latest library from the phpmailer official website and configured it according to the test file that comes with it. sockets is also supported in php. ini. I have tried a lot of online materials, but I still cannot. Therefore, I would like to thank you for your advice !!! & L PHPMailer error: cocould not instantiate mail function.
I downloaded the latest library from the phpmailer official website and configured it according to the test file that comes with test. sockets is also supported in php. ini. I have tried a lot of online materials, but I still cannot. Therefore, I would like to thank you for your advice !!!

 /**
* Simple example script using PHPMailer with exceptions enabled
* @package phpmailer
* @version $Id$
*/

require '../class.phpmailer.php';

try {
$mail = new PHPMailer(true); //New instance, with exceptions enabled

$body             = file_get_contents('contents.html');
$body             = preg_replace('/\\\\/','', $body); //Strip backslashes

$mail->IsSMTP();                           // tell the class to use SMTP
$mail->SMTPAuth   = true;                  // enable SMTP authentication
$mail->Port       = 25;                    // set the SMTP server port
$mail->Host       = "smtp.163.com"; // SMTP server
$mail->Username   = "****@163.com";     // SMTP server username
$mail->Password   = "***";            // SMTP server password

//$mail->IsSendmail();  // tell the class to use Sendmail

$mail->AddReplyTo("***@163.com","First Last");

$mail->From       = "***@163.com";
$mail->FromName   = "phpmailer";

$to = "***@qq.com";

$mail->AddAddress($to);

$mail->Subject  = "First PHPMailer Message";

$mail->AltBody    = "To view the message, please use an HTML compatible email viewer!"; // optional, comment out and test
$mail->WordWrap   = 80; // set word wrap

$mail->MsgHTML($body);

$mail->IsHTML(true); // send as HTML

$mail->Send();
echo 'Message has been sent.';
} catch (phpmailerException $e) {
echo $e->errorMessage();
}
?>

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Give your

Maybe the required php version is too high, right?
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// $ Mail-> IsSendmail ();
By default, the system's mail function is used to send emails. Is that the reason.