She started the email in mid-January 2009. She was confirmed Jan. 15, 2009 for Secretary of State.
Clinton had the private server prior to this from 2007, but she didn’t use it.
She only moved to it once she was confirmed Secretary of State. So she wasn’t using an old email ‘for convenience’.
The only reason one would do this would be to have complete control over emails.
Here’s a link to the FBI documents that were released today.