Mail.php的引用路径错误

在安装了cpanel的centos 6.7上发送电子邮件时遇到问题。我认为Mail.php引用路径有问题，但我不知道如何更正。Mail.php文件位于此处：/home/userfolder/php/Mail.php（我已经安装了以下PEAR包：Auth_SASL、Mail、Net_SMTP、Net_Socket）我得到的错误是：致命错误：在第14行的home/userfolder/public_html_sendmail.php中找不到类"邮件"

<?php
ini_set("include_path", '/home/userfolder/php:' . ini_get("include_path") );
$from = "Sandra Sender <info@domain.com>";
$to = "Ramona Recipient <info@domain.com>";
$subject = "Email";
$body = "Hi,'n'nHow are you?";
$host = "mail.domain.com";
$username = "username";
$password = "password";
$headers = array ('From' => $from,   'To' => $to,   'Subject' => $subject);
$smtp = Mail::factory('smtp',   array ('host' => $host,     'auth' => 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>");  
    }
?>