Hillary Clinton should have kept her personal and public emails separate for transparency and safety. It is not for her to decide whether it is safe to send emails over a private server, and as a public figure she is responsible for the country's safety, not just her own. The protocols were set up by people who know more about security than she does.
There is no difference in strength of security between private servers and government servers. They all run the same encryption standards. In fact, it may be safer as any government server may be a higher class of target to hackers than a private and anonymous one would be. Hillary may have made a public no-no but I don't think she put the security of the nation at risk.
I do not believe that Hilary Clinton's use of private server and e-mail account has been a breach of national security. I believe that everyone, even politicians, are entitled to their privacy. I do not think that anything she could have done on there server would have put our nation at risk.
Hillary Clinton's use of a private server and e-mail account did not breach national security. Those who held her position previously did the same thing. Although there have been many allegations, these have come from her political enemies. In spite of this, no one has been able to prove that national security was breached.