problem in sending mail by gmail smtp in server but works fine in localhost
<?php

   require_once "Mail.php";

    $from = "username@gmail.com";
    $to = "username@yahoo.com";
    $subject = "Hi!";
    $body = "Hi,nnHow are you?";

    $host = "ssl://smtp.gmail.com";
    $port = "465";
    $username = "username@gmail.com";
    $password = "*****";

    $headers = array ('From' => $from,
      'To' => $to,
      'Subject' => $subject);
    $smtp = Mail::factory('smtp',
      array ('host' => $host,
        'port' => $port,
        '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>");
     }

?>