The man who was State Department inspector general from 2005 to 2008 said, “I would have been stunned had I been asked to send an email to her at a personal server, private address. I would have declined to do so on security grounds and if she had sent one to me, I probably would have started an investigation.”
There was no Inspector General during the time Clinton served in the State Department.
The White House acknowledged earlier this year that they had been aware of Clinton's private email address and that President Obama had exchanged emails with her. To be clear, everyone knew she had a private email address, no on wondered what server it was on. The fact that it didn't raise any red flags for anyone makes me wonder if she wasn't the only one in the administration using private email to avoid FOIA searches.