Of course they knew…
Check it out:

Yes, it seems the Obama White House knew about the Clinton’s private emails–and knew it would be a huge problem–but decided to defer action on that item to her staff. Oh, and they found out about this … last August. White House, State Department officials, and members of Hillary’s entourage knew that House Republicans had stumbled upon this information through the select committee investigating the Benghazi terrorist attack. Their decision was to remain tight-lipped about it