I'm not accusing her of a crime. I'm accusing her of either incompetence or horrible judgement, given her position as one of the few Original Classification Authorities in the executive branch ( https://www.whitehouse.gov/the... SecState is the first Department mentioned. ). She should have known better. Maybe she did know better, but chose not to do better - that'd be worse.
Further, she was expected (one could even say "ordered by the President") to take Classification Training annually: https://www.whitehouse.gov/the... section 1.3d:
"All original classification authorities must receive training in proper classification (including the avoidance of over-classification) and declassification as provided in this order and its implementing directives at least once a calendar year. Such training must include instruction on the proper safeguarding of classified information and on the sanctions in section 5.5 of this order that may be brought against an individual who fails to classify information properly or protect classified information from unauthorized disclosure. Original classification authorities who do not receive such mandatory training at least once within a calendar year shall have their classification authority suspended by the agency head or the senior agency official designated under section 5.4(d) of this order until such training has taken place. " You can't argue that she was unfamiliar with this issue.
Even more, as a former FLOTUS, as a former Senator, and ESPECIALLY as Secretary of State (analogous to a Foreign Minister in other countries), she should CERTAINLY expected that her communications would be a primary target by foreign adversaries. She had high-level conversations with advisers, communications with/about other foreign leaders and diplomats, national policy issues, internal State Department policy issues. We already know the NSA is interested in this kind of stuff for other countries (most recently the shit with Israel) ; pretty much everyone else would love to have this information on the US as well. We're all self-important geeks here who think the NSA is watching all of us as we play video games and post on Slashdot and Reddit. How can anyone give a pass to a Secretary of State, who has real, LEGIT reasons to suspect she'd be targeted?
And then there were the political games she's been playing in the aftermath, instead of handing shit over, lawyering up and taking her lumps if necessary, and moving on. If it cost her an opportunity at the Presidency, oh well, that's what accountability at that level means; its not as if she didn't have POTUS aspirations back then. The world knew it. (More of a reason to suspect she'd be targetted by other intel services, actualy). Instead, she avoided having to turn stuff over as long as possible, tried deleting stuff, hand-selected things to turn over, plays this stupid shrugging game, insults our intelligence by saying "“It was on property guarded by the Secret Service and there were no security breaches. So I think that the use of that server certainly proved to be effective and secure.”". (Yes, she said that. http://www.wired.com/2015/03/h... )
Even if every single email she had on there was born and legitimately unclassified, they were at very least sensitive. And a bunch of unclassified things can be considered classified in aggregate. "(e) Compilations of items of information that are individually unclassified may be classified if the compiled information reveals an additional association or relationship that: (1) meets the standards for classification under this order; and (2) is not otherwise revealed in the individual items of information." (from one of the Executive Order links above as well)
So incompetence or bad judgement: I don't know which. Criminality aside, there are other very strong reasons for her to NOT be a leading candidate for presidency. The same reasons Trump shouldn't be a leading candidate either, actually: Character and judgement.