Codeigniter电子邮件确认

我是新来的Codeigniter。我想创建一个登录&注册页面在我的项目。登录和注册是成功的，但如果我想确认电子邮件，它总是说404未找到如果点击验证链接。这段代码有什么问题?帮我

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class Voter_model extends CI_Model
{

 function __construct()
 {
      // Call the Model constructor
      parent::__construct();
 }
 //get the username & password from tbl_usrs
 function get_user($username, $password)
 {
      $sql = "select * from user where username = '" . $username . "' and password = '" . $password . "' and status = '1'";
      $query = $this->db->query($sql);
      return $query->num_rows();
 }

 //insert into user table
function insertUser($data)
{
    return $this->db->insert('user', $data);
}
//send verification email to user's email id
function sendEmail($to_email)
{
    $from_email = ''; //change this to yours
    $subject = 'Aktivasi Akun';
    $message = 'Dear'. $username .'<br /><br />Please click on the below activation link to verify your email address.<br /><br /> 
  '. site_url('voter/voter_register/verify') . md5($to_email) . '<br /><br /><br />Thanks<br />Admin, Gus bala';
    //configure email settings
    $config['protocol'] = 'smtp';
    $config['smtp_host'] = 'ssl://smtp.googlemail.com'; //smtp host name
    $config['smtp_port'] = '465'; //smtp port number
    $config['smtp_user'] = $from_email;
    $config['smtp_pass'] = ''; //$from_email password
    $config['mailtype'] = 'html';
    $config['charset'] = 'iso-8859-1';
    $config['wordwrap'] = TRUE;
    $config['newline'] = "'r'n"; //use double quotes
    $this->email->initialize($config);
    //send mail
    $this->email->from($from_email, 'Admin Evoting');
    $this->email->to($to_email);
    $this->email->subject($subject);
    $this->email->message($message);
    return $this->email->send();
}
//activate user account
function verifyEmailID($key)
{
    $this->load->database();
    $data = array('status' => 1);
    $this->db->where(md5('email'), $key);
    $this->db->update('user', $data);
}
}?>