Enquiry with custom find type

gistfile1.php

<?php
// the Model

class Enquiry extends AppModel {
  public $_findMethods = array('junk' => true);

  protected function _findJunk($state, $query, $results = array()) {
    if ($state == 'before') {
      $query['conditions']['Enquiry.mailbox'] = 'JUNK';
      return $query;
    }
    return $results; 
}