The Federal Records Act says that government business on email must be archived on government servers. The Espionage Act says that classified information may not go out on unsecured or unauthorized networks. The law is that once something is under subpoena if you delete it, that is obstruction of justice.
Hillary and her staff did all of this countless times. When asked about it the reflexive answer was not just to simply tell the truth, it was to invent the best possible answer to benefit them. This of course, is also obstruction because they know that the FBI and Congress will be asking these very questions. No indication of just telling the truth is suggested.
You can real the email HERE: