If you want a deep dive into what matters and what doesn't regarding Hillary Clinton's emails (primarily) and Trump's classified documents, then read on. If not, feel free to skip. I have in the past worked in email and records administration for Department of State, so I know of what I speak.
Hillary Clinton intentionally broke US Government and State Department policy by not submitting relevant emails from her private unclassified mail server to the DoS archive. Every high-level employee at State knows the requirement to preserve anything that is defined as a "record" (an official document of government business or transaction). All of her staff would be aware of this.
But, I can tell you from first-hand experience, if a Presidential appointee does not wish to comply with the rules, there is little a civil service employee can do to make it happen. Unless you want to make a complaint to the Inspector General - and we saw in the Trump Administration what happened to people who took that route.
What's more, the very use of the private server indicates this was not an oversight, but her intent from the very beginning. She clearly wanted to prevent another Whitewater and not leave documents around available for a future fishing expedition.
It was not until this omission was made public, and Congress demanded copies of emails that she submitted them to the State Department.
And even then, she delivered them as printed copies - the most labor intensive way to store them. She could have done it electronically and they would have been easily added to the archive and searchable. Again, this seems not to be a mistake, but her intention was to make this as difficult as possible. These records then had to be scanned and error-checked before they could go in to the system - a process that was very labor and time intensive - we are talking about many weeks.
That being said, the charge that she mishandled classified information was all smoke and mirrors.
While she deserved rebuke for her handling of her unclassified email - the vast majority of official State Department business is conducted on the classified system, where official messages are still sometimes called "cables". And what seemed to go unreported is that all of her classified messages were sent to the archive and available to Congress from the beginning. So, from the beginning of the Benghazi investigation(s), Congress had all of those messages. And if you want to know what the official communication was during that tragic event, it was all in the classified system.
Finally, the charge that classified information was found on her private server - that is a huge and deliberate mischaracterization. It rests on the difference between classified information and classified documents.
Classified documents (either printed or in the classified email system) are marked with their classification on every page. It is impossible to mistake what they are. What's more, there is no network link between the two systems. You can't "accidentally" copy documents from one system to the other. They are different computers, usually in different rooms. (Classified computers can only be in physically secured rooms.)
Classified information is something different. It is information that an agency has designated as classified and should only be discussed in the classified system.
Here's the problem - different agencies have different opinions on what information is classified and what isn't. And since email discussions go on between high and low ranking individuals in multiple agencies, one really has no way of knowing if someone somewhere in the US government has decided that data is classified.
What became controversial for Hillary is that there were some topics discussed in her unclassified emails that other agencies decided after-the-fact should be restricted to the classified system only. None of these emails were sent by Hillary, by the way, she was just on the receiving end, so they appeared on her server.
But, here's the thing - this is no different than what happens on the State Department Unclassified email system every day. This has nothing to do with having a private server. The data would have been just as out in the open on unclassified State Department email as on Hillary's server.
This was a total red herring publicized to make Clinton a punching bag in public.
Contrast this with President Trump who took physical documents marked "Classified" on every page out of the White House and down to his private home in Florida. Those documents can not ever leave a secured enclave or it breaks the system as a whole.
That is not only inexcusable, it directly damages US security.
And, in addition to that - why aren't those documents in the official archive?