Manafort tried using a clever technique for hiding his crimes, but it didn’t work.
My impression of Manafort is that he’s not too bright. Although this technique is an ingenious little dodge, it’s a very weak method for hiding emails and has been around for ages. How could Manafort possibly think that the FBI wouldn’t be all over this? All that he’s managed to do by using this technique is to further implicate himself, demonstrating that he knew he was doing something illegal.