Empty token values when enablinig the module

I created small custom module which defines user registration emails as the multidomain emails.
The module source:

function mymodule_variable_info_alter(&$variables, $options) {
  $list = array(
    'user_mail_register_admin_created_[mail_part]',
    'user_mail_register_pending_approval_[mail_part]',
    'user_mail_register_no_approval_required_[mail_part]',
    'user_mail_status_activated_[mail_part]',
    'user_mail_status_blocked_[mail_part]',
    'user_mail_cancel_confirm_[mail_part]',
    'user_mail_status_canceled_[mail_part]',    
    'user_mail_password_reset_[mail_part]',
  );
  foreach ($list as $name) {
    if (isset($variables[$name])) {
      $variables[$name]['multidomain'] = TRUE;
    }
  }
}

After enabling this variables as multidomain in the Domain Variables tab and then open the "Account settings" interface to edit the user emails, the email values generated are without the tokens.