Back here, I linked you to an article by Joe Conason explaining that in The Great Hillary Clinton E-Mail Scandal, the total number of e-mails that turned out to be marked "classified" was zero. So I feel I should also link you to a fact-check by Glenn Kessler who goes into great detail on the matter. The bottom line seems to be that she did things wrong but they turned out to be minor whereas he did some things wrong that sound pretty major. (Actually, the bottom lines seem to be to be that she cooperated fully with the investigation and that the Trump Administration could not muster up enough of a case to formally charge her. But read it for yourself.)