The likely Democratic presidential nominee learned this week that she will not face criminal charges over her use of private email.
The FBI said that although she had sent and received sensitive material there was no evidence of intent.
Now that inquiry is over, the State Department will reopen its review.
As well as the former secretary of state, it will also include some of her former aides, all of whom have now left the department.
Continue reading: US State Department restarts Hillary Clinton email probe – BBC News