From the BBC:
Mrs Clinton said no classified material was sent from the private account and said her use of personal email was permitted by the state department.If she'd fully complied with every rule she wouldn't have used a private email for one of the most sensitive jobs in the world. Did you know that not all sensitive information is classified, that snippets of unclassified data can be combined into classified knowledge, and that, depending upon your job, it can be really easy to take classified information for granted and let it out in conversation with close family (this is why, if you have a spouse, your spouse must be eligible for whatever clearance you receive, even though they'll likely never receive a clearance).
"I fully complied with every rule," she said.
But she said she had discarded thousands of personal emails, including ones about planning her daughter's wedding and her mother's funeral.
In addition, given her previous track record, anything she says has to be taken with a (large) grain of salt. I'll believe that no classified information was sent using her private email, that she really turned over all the relevant emails and that she hasn't already deleted all the incriminating emails when she proves it in a court of law.