Hillary Clinton likely violated some federal statues by using a private email server while serving as secretary of state. Furthermore, Clinton likely put national security at risk, because her server was a golden target for foreign hackers and adversaries of the United States. However, it is unlikely that any of Clinton's supporters will care, nor will a majority of Americans care when it is time to vote in November. In short, it is probably better for the State Department to just forget about the email scandal and move on.
Although Hilary Clinton flouted several rules by handling confidential and sensitive governmental data using her personal e-mail address it does not appear that there is anything further to gain by pursuing the case any longer at the cost to US taxpayers. No further action should be taken because there is little to gain.
While it is clear that Secretary Clinton used incredibly poor judgement in using a personal server while conducting government business, the continued investigations into an issue that has been obsessively researched, debated, and reported is beginning to have diminishing returns. At this point, continued investigation serves no purpose to the country and is clearly just a political football in the midst of a heated presidential race.
The time and money spent on the Clinton email investigation has been quit extensive and the State Department needs to focus on other priorities. The conclusion of all the email investigation shows poor judgement but not criminal behavior. There were other government officials that followed the same course as Hillary but we can not waste any more of our government resources on this topic.