The problem is any emails sent to or from Hillary's personal server to another private email address never went through the State Dept. There's no way to know about those, unless the NSA happened to be watching those private emails.
So her private server was mainly done to provide a private communications network that the State Department could not access. She got caught because she was lazy and wanted State Department emails also sent there. Or she needed that as cover to justify the private server. Was she running a covert Presidency ? Is that how the Middle East and Africa have gotten so messed up ?