PHP使用pear_smtp发送简单邮件

<?php  
 require_once "vendor/autoload.php";  
   
 $from = "test<test@163.com>";  
 $to = "test <test@outlook.com>";  
 $subject = "Hi!";  
 $body = "Hi,\n\nHow are you?";  
   
 $host = "smtp.163.com";  
$port = "25"; 
 $username = "test@163.com";  
 $password = "test123";  
   
 $headers = array (&#39;From&#39; => $from,  
   &#39;To&#39; => $to,  
   &#39;Subject&#39; => $subject);  
 $smtp = Mail::factory(&#39;smtp&#39;,  
   array (&#39;host&#39; => $host,  
     &#39;port&#39; => $port,  
     &#39;auth&#39; => true, 
    // &#39;debug&#39;=>true, 
     &#39;username&#39; => $username,  
     &#39;password&#39; => $password));  
   
 $mail = $smtp->send($to, $headers, $body);  
   
 if (PEAR::isError($mail)) {  
   echo("<p>" . $mail->getMessage() . "</p>");  
  } else {  
   echo("<p>Message successfully sent!</p>");  
  }  
 ?>