From Politico:

In this case, which is truly unprecedented, no matter what Secretary Clinton would have one believe, she managed successfully to insulate her official emails, categorically, from the FOIA, both during her tenure at State and long after her departure from it—perhaps forever. “Nice work if you can get it,” one might say, especially if your experience during your husband’s presidency gives you good reason (nay, even highly compelling motivation) to relegate unto yourself such control if at all possible.