static IterableIterator<Message> mail_iterateFolder(final Folder folder) ctex {
  mail_openReadOnlyIfClosed(folder);
  final int n = folder.getMessageCount();
  ret new IterableIterator<Message>() {
    int i = n;
    public bool hasNext() {
      ret i >= 1;
    }
    
    public Message next() ctex {
      ret folder.getMessage(i--);
    }
  };
}