Bernie had it right.
Note: Hillary's indiscretions with her emails are one thing; accusations of serial murder are entirely different and will not be tolerated here. She is a private citizen and she can sue for slander, and me as well if I permit it on this thread.
Her problem was a familiar one to anyone who has work emails that are subject to microscopic review; in my case, it was for possible shareholder litigation.
I will suggest a way of thinking about this as regards Hillary's job as Secretary of State. There's a general discussion, some comments about the specifics as regards 'government work', and specifics about Hillary's case.
The uniquely worst thing you can do (Rule 0) is leave something out there which sounds like an admission of guilt.
There are many lesser bad things you can do when you are faced with a bad situation.
Here are a couple bad situations:
1) You are in a place, or even a temporary situation for technical reasons, where access to your business server is not available and you must communicate. It happens. Passwords expire, servers go down, you have to submit a file in the next two minutes (cf. Broward County).
2) You want to have an off-the-record discussion that has some relationshp to work subject matter, but physically speaking to each other is not possible for some reason (nor Skype, or whatever--see No. 1), and your phone line is not secure.
In the case of 1), if you have to resort to using your personal email, you are technically violating your privacy rules/code of conduct/legal restrictions. Use of a secure service within the personal email helps confine the issue but does not eliminate it. Any penalties depend on the circumstances but are usually minor unless there is evidence of malign intention. It usually involves improving your backup communication methods. Whether you delete sooner or later or never is not particularly relevant--generally speaking, you should expect privacy on your personal emails without a warrant, and you should assume whatever there was, it can all be found. The right thing to do is for the user of the email to review instances and report classified material as such, so its use (such as re-purposing or forwarding) can be controlled.
In the case of 2), the grey areas are many and diverse. Whether you did anything wrong or not depends on what is discussed, with whom, and what level of sensitivity it has.
I never had much problem with 2), except possibly regards HR things. In the case of the government, for some reason (historical?) all emails on the work server are considered official documents (as are, more absurdly, tweets from official twits)
If you are having a "work problem" in either case 1) or 2), the sensitivity is amplified by Rule 0.
.In the case of the US Government, there is a very aggressive posture toward classifying, a very laid-back one toward de-classifying, and a lot of vague lines about what needs to be classified and how much, and when. It's a jobs thing.
a) Jet-Lag is a real problem, when you're putting in big miles, as any Secretary of State needs to do, if the job is being performed properly. When you get back "home", you need quiet time, preferably away from the office, to recover. We're talking 48-72 hours, after an ambitious itinerary with heavy timezone changes or other physical demands at sites abroad.
b) There are a lot of sensitive discussions that do not themselves directly refer to or use classified information. In her case, having to do with diplomacy, protocol, budget or HR things. Use of private email is "discouraged".
One obvious approach to the problem is to always any type 2) activity on the work servers, including a fair amount of classified information in every communication), that way, the redactors will get at it and FOIA readers will just see a bunch of blacked-out gibberish. You can do it, but people will hate you, and that reduces your effectiveness. People respond better when they don't have to watch their backs. And there is 1), also, which could affect timely communication. You can use code words, but ones that refer to classified things are still going to be classified.
Hillary's solution cut corners, to be sure. While she used official channels when available, and seems to have successfully avoided bringing in classified material, she wanted to use her private server--which was secure, particularly so for being off the books--when she was at home. Some things that she communicated were later classified, which shows some hygiene was being performed. Apparently she was not advised she must improve her backup communication methods--that's on her, somebody like the Inspector General office (The Grand Inquisitor), and ultimately, on Obama, too.
I am quite certain that when events like the Benghazi!! tragedy occurred, there were discussions that had to stay off the record that were relevant to the challenge posed by them-unfortunately, in the case of the Libyan attack, it seems those were mostly after the fact. If they had to be done by email, and in the dead of night or something, they might be out there in the private server. So, the sin is really hiding from the record-keepers and review officers stuff that was meant to be hidden.
We can draw whatever conclusions we want about what was hidden and not found, or left classified, or redacted on further review. These are her private documents; maybe there will be a warrant or some kind of civil suit, under terms that bring more out into the open, at some point (I doubt that will happen).
The official reviews have been conducted by the appropriate parties and no indictable offense was found. Historians may have a shot at some of the classified stuff, someday.
And, now, what about Trump? When does he show us his?* Effective scrutiny of his past misdeeds is sadly lacking. We think we have seen everything, because what we have seen is so awful. But, there will be much more disclosed before long. The natural thing to do when you have something to hide is to deflect the subject, to provide distraction. Yes, that is what he does, isn't it?
I'm not expecting anything impeachable, not because he's not culpable, but because impeachment is entirely a political process--there are guidelines, but the field is pretty much open. Many things, like Clinton's classified emails, and quite possibly much of Mueller's final report (what exactly will be a battlefield in courts in private session) will be protected under executive privilege, and we now seem pretty sure he can not be indicted (until after he leaves office; may it be soon).
The stuff we know about Trump would have precluded any responsible Presidential nominee from considering him as a running mate. (We've come a long way since Spiro Agnew.) I think there's a fair chance we will overcome his shading, deflection, defiance, lying (he said he would release his tax returns), thus allowing the public to know what we need to know about him before we decide whether to renew his contract.
This time. No mistakes this time.
*I've heard it's kind of wrinkled and fungusy-looking....
+(to the tune of Punky's Dilemma..."Wish I was a Kellogg's Cornflake/Trying to get the most out of a toaster")