Most people in normal IT and media are not fully privy to the requirements of NSA or other 3 letter agency “secure” communications for transmission of TS and above that say a Secretary of State might need to do his/her job.
This isn’t just encryption schemes between servers and/or end users - it is a comprehensive and rigorous process that necessitates separation of secure and nonsecure traffic from end to end, and complete physical layer encryption from end-to-end/
In other words, to just say her email/server setup was ‘secure’ is most likely bullshit, further complicated by the fact there were many email accounts on her server. And to say or imply that all this could have comingled secure and unsecure person traffic is patently ludicrous. Her ‘setup’ did not have, nor could have that capability, frankly.
The Classified networks that the State Department uses: SIPRNet and JWICS aren’t even physically connected to the internet, so email on those systems cannot be sent to a private email server. She could certainly discuss classified or sensitive information in email and likely did so, but she is probably at least technically correct when she claims to have never sent “classified documents”
One has to wonder if her email server was backed up or archived regularly. Is it not standard practice to backup crucial hard drives every now and then ? Why do we not even know who was the IT tech providing support for the server ?