500 Internal Server Error after changing gmail password

Code:
<?php

require 'application/third_party/email/PHPMailerAutoload.php';



$mail = new PHPMailer;



//$mail->isSMTP();                                      // Set mailer to use SMTP

$mail->Host     = 'smtp.gmail.com';                       // Specify main and backup server

$mail->SMTPAuth = true;                               // Enable SMTP authentication

$mail->Username = '[email protected]';                   // SMTP username

$mail->Password = 'Demo123#';               // SMTP password

$mail->SMTPSecure = 'ssl';                            // Enable encryption, 'ssl' also accepted

$mail->Port = 587;                                    //Set the SMTP port number - 587 for authenticated TLS

$mail->setFrom('[email protected]', 'header name');     //Set who the message is to be sent from

$mail->addAddress('[email protected]');  // Add a recipient

$mail->WordWrap = 50;                                 // Set word wrap to 50 characters

$mail->isHTML(true);                                  // Set email format to HTML



$mail->Subject = 'Here is the subject';

$mail->Body    = 'This is the HTML message body <b>in bold!</b>';

$mail->AltBody = 'This is the body in plain text for non-HTML mail clients';



//Read an HTML message body from an external file, convert referenced images to embedded,

//convert HTML into a basic plain-text alternative body

$mail->msgHTML('Hi, This is my test email');



if(!$mail->send()) {

   echo 'Message could not be sent.';

   echo 'Mailer Error: ' . $mail->ErrorInfo;

   exit;

}



echo 'Message has been sent';

?>