Hillary Clinton didn't just have a private "email account."
She owned a registered domain, (clintonemail.com) and served the domain from a local server, inside her residence, giving her 100% administrative control over email accounts, records, and traffic. This is quite a bit different from having a private "account" - such as a gmail, yahoo, or even an isp hosted account such as sbcglobal.net or a Time Warner Road Runner account.
In Hillary's situation, there was not even a web host to limit her activity. The domain resolved directly to the physical equipment located in her residence.
For the record, in the history of U.S. Government;
this has NEVER, EVER BEEN DONE BY ANYONE ELSE.
The hardware and software requirements for running ones own mail server are negligible. Email is a rather arcane application. The email protocol was established in the early days of the internet and was written to run on server systems created when a "gigabyte" was a theoretical term and most equipment ran on less than 4 megabytes of RAM. Much of the email traffic on the internet is still served by either Sendmail, Postfix, or Qmail. All open source, all freely available at no cost. The total hardware, software, and tech labor required to set up such a system could easily be done for under $2,000.00
With this system in place, Hillary can create as many email accounts as she chooses, send and delete email permanently, and conceal anything she pleases.
Remember that the only permanent location of these emails are on the physical hard drive in the local computer. In the event she wanted to delete emails, or even the record of entire email addresses, she could simply delete them from the current drive; then back up the accounts and emails she wished to preserve, destroy the original disk drive, install a new clean drive, then restore the accounts from back up.
The new drive will not even have a relic of the previously deleted emails and deleted email accounts.
This fact renders the idea of investigating her server - meaningless. No person who intended to conceal evidence on a hard drive, would still have any such evidence there. And no person that didn't want the ability to conceal email information - would ever set up such a system.
There seems to be a growing clamor for Hillary to "turn over the server." This is a mistake. It could only serve to create one more scandal that ends with "no evidence."
The crime here was setting up the system - as it was set up - so that verification was impossible. It must be noted that every governmental office that communicated with Hillary at "clintonemail.com" is complicit in this crime. To pretend that investigating "the server" at this point, could yield any evidence of wrongdoing - is a fools game.
If there are emails out there that implicate Hillary in any wrongdoing, they currently only exist on the recipients mail server. If one were serious in finding anything - that would be the direction of investigation.
The larger point is, that Hillary Clinton conducted business as the Secretary of State of the United States of America - for four years; through an obviously rogue email system - and NOBODY did anything about it.
Even now, it's likely that nobody ever will.