...i figure she must of received mail from underlings in state and people in the senate/house/etc that prolly sent her classified material....
True, she had to deal with routine actions through the State Dept, but for truly important info, she dealt only through her server.
The telling fact here is how long it has taken the FBI to start securing these points of contact, giving many people a chance to cover their tracks, clean their hard drives. Destroy evidence.