PHP使用pear_smtp发送简单邮件

PHP自带的mail函数比较蛋疼，在win下配置了sendmail还是无法发送邮件。而使用第三方的pear/mail可以直接通过smtp连接邮件发送服务器。如(smtp.163.com)。从而没有必要在本机上安装sendmail等类似软件。
确保PEAR Mail包已经安装。 
composer安装方式:composer require pear/mail pear/net_smtp

参考:
http://email.about.com/od/emailprogrammingtips/qt/PHP_Email_SMTP_Authentication.htm
http://stackoverflow.com/questions/2284468/problem-with-php-pear-mail

1. [代码]非加密方式    

<?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 ('From' => $from,  
   'To' => $to,  
   'Subject' => $subject);  
 $smtp = Mail::factory('smtp',  
   array ('host' => $host,  
     'port' => $port,  
     'auth' => true, 
    // 'debug'=>true, 
     'username' => $username,  
     'password' => $password));  
   
 $mail = $smtp->send($to, $headers, $body);  
   
 if (PEAR::isError($mail)) {  
   echo("<p>" . $mail->getMessage() . "</p>");  
  } else {  
   echo("<p>Message successfully sent!</p>");  
  }  
 ?>