Do you REALLY think that the only people with whom the US Secretary of State communicates in the course of her professional duties are people INSIDE her own department? Not a single person in another country, not a single person in a think tank, another federal agency, not a legislator, nobody? Only the people directly under her authority at State?
Remember that one of the events leading to this was an email leaked by Romanian hacker Guccifer, who cracked into the private mailbox of Clinton confidant Sydney Blumenthal. He is advising her on sensitive intelligence (re: Europe, the Muslim Brotherhood, and much more) in a series of "highly confidential" messages. Those messages, by definition, never saw the State Department's mail servers or archiving systems as required by federal regulations in place at the time. Why? Because he was providing the Secretary of State with that sensitive information via a private mailbox on an server kept in her house, the contents of which government archivists will never have their legally mandated opportunity to review for what is, and is not government-related communication.
She went out of her way to keep such communications out of the hands of the archives. You can't possibly be confused on this subject.
Regardless, she did NOT claim that the State department had all of her records. If she held that position, then why did she (after the existence of her private stash had been discovered) agree to provide to State (long after she'd left office) 50,000+ printed out pages of emails once pressed on the matter years after she left office and there was no denying it? Why didn't she just refer the people seeking the records to the CC's you're saying were adequante? You know why: because she knew it would be BS to imply that was the extent of her legal public records. But of course we get ONLY her opinion on what was or was not relevant. Everything else has been deleted, says her lawyer. But ... in those 50,000+ pages are gaps of weeks and months. Are you really suggesting that she exchanged no email, in her role as Secretary of State, for months at a time?