function unsubscribe($data, $form) {

      $email = $this->urlParams['Email'];
/***********************************************/
//      Change to get Data by ID
//      $member = DataObject::get_one( 'Member', "Email = '{$email}'" );
      $member = DataObject::get_by_id( 'Member', $email );
/***********************************************/

      if(!$member){
/***********************************************/
//      Change to get Data by ID
//    $member = DataObject::get('Member', "`EmailAddress` = '$email'");
   $member = DataObject::get_by_id('Member', $email);
/***********************************************/
}

if( $data['MailingLists'] ) {
foreach( array_keys( $data['MailingLists'] ) as $listID ){
      
      $nlType = DataObject::get_by_id( 'NewsletterType', $listID );
      $nlTypeTitles[]= $nlType->Title;
$this->unsubscribeFromList( $member, DataObject::get_by_id( 'NewsletterType', $listID ) );
}

$sORp = (sizeof($nlTypeTitles)>1)?"newsletters ":"newsletter ";
//means single or plural
$nlTypeTitles = $sORp.implode(", ", $nlTypeTitles);
    $url = "unsubscribe/done/".$member->Email."/".$nlTypeTitles;
        Director::redirect($url);
} else {
    $form->addErrorMessage('MailingLists', _t('Unsubscribe.NOMLSELECTED', 'You need to select at least one mailing list to unsubscribe from.'), 'bad');
   Director::redirectBack();
}
}

...

class Unsubscribe_MailingListForm extends Form {

   protected $memberEmail;

   /****Create an ID-Environment variable****************/
   protected $memberID;
   /***********************************************/

   function __construct( $controller, $name, $member, $email ) {

   if($member) {
      $this->memberEmail = $member->Email;

      /*****Load the Member.ID to the variable**************/
      $this->memberID = $member->ID;
      /***********************************************/
   }

$fields = new FieldSet();
$actions = new FieldSet();

if($member) {
    // get all the mailing lists for this user
    $lists = $this->getMailingLists( $member );
} else {
   $lists = false;
}

if( $lists ) {
    $fields->push( new LabelField('SubscribedToLabel', _t('Unsubscribe.SUBSCRIBEDTO', 'You are subscribed to the following lists:')) );

foreach( $lists as $list ) {
$fields->push( new CheckboxField( "MailingLists[{$list->ID}]", $list->Title ) );
}

$actions->push( new FormAction('unsubscribe', _t('Unsubscribe.UNSUBSCRIBE', 'Unsubscribe') ) );
} else {
    $fields->push( new LabelField('NotSubscribedToLabel',sprintf(_t('Unsubscribe.NOTSUBSCRIBED', 'I\'m sorry, but %s doesn\'t appear to be in any of our mailing lists.'), $email) ) );
}

parent::__construct( $controller, $name, $fields, $actions );
}

function FormAction() {
      /**** Change the FormAction Button to submit the ID******/
      //return $this->controller->RelativeLink() . "index/{$this->memberEmail}?executeForm=" . $this->name;
      return $this->controller->RelativeLink() . "unsubscribe/{$this->memberID}/";
      /***********************************************/
}

protected function getMailingLists( $member ) {
// get all the newsletter types that the member is subscribed to
return DataObject::get( 'NewsletterType', "`MemberID`='{$member->ID}'", null, "LEFT JOIN `Group_Members` USING(`GroupID`)" );
}
}