I don't think this is completely understood by many, they've found classified information in the email traffic at TS/SCI level. Those emails weren't necessarily sent by Hillary Clinton but it makes it all very serious. Whether is was marked or unmarked or whatever it was it was sitting there and somebody is going to be in trouble. They don't just walk away from this kind of thing, its the kind of thing that people go to jail for pretty commonly.
I've personally seen a group of security people come take a coworker's pc away on a dolly and then watched him sit for a couple of years in a unsecure area doing pretty much nothing until they cleared him and restored his access. It is definitely a long process.
Hillary was either devious or incredibly stupid or both for setting up a private email server at home and then conducting State Dept business on it with the intention of controlling what information would be retained later. Its a complete violation of government document retention laws. Then finding sensitive classifed email in traffic deemed by Hillary to be retained for the public but 30,000 other messages deleted from the same server is really beyond comprehension. Its a bit like Travelgate, Whitewater and Clinton's dealings with commodities brokers and this huge corrupt multimillion dollar "foundation", none of it passes the smell test.
Given Hillary's complete failure as Secretary of State (Benghazi, Russian "reset", Syrian, Libyan and Egyptian debacles) and her non-performance as a US Senator combined with a long history of sketchy behavior it is difficult to see how she could become President. It is possible though and one must never underestimate the self-destructive power of the American voter.