That much is obvious. But what was she hiding?
The server, if you look at the usage, became a catch-all solution device.
An example. When Hillary was finally offered the Sec of State job....she prepared a list of people that she was bringing on. Sid Blumenthal was on the list. The WH looked at people, and Sid was the ONLY person on the list denied employment. Four weeks go by, and Hillary has a second list of contractors who she wanted hired...Sid Blumenthal was on that list....he was again the ONLY person denied.
What did Hillary do? She used the Clinton Foundation to hire the guy. Guess who was given access to her email account on the server? Sid. This is an item which rarely gets discussed.
The secret and top secret material cut and pasted onto her emails? All read by Sid.
I think you can prepare a list of thirty-odd problems that she had, and the private email server fixed all of those issues. Even today, she probably has another private server in the same bathroom, and it’s her way of communication.