Hillary Clinton has told reporters she used private emails out of “convenience” during her time as secretary of state.
But Mrs Clinton said it “would have been better” to have two accounts to separate work and personal emails.
The issue of whether Mrs Clinton breached federal records rules has gained attention as she is expected to announce a run for president.
She is seen as a top contender for the 2016 Democratic nomination.
Mrs Clinton had planned to spend March talking about women’s issues – including at a UN speech on Tuesday – before announcing her candidacy in early April, the Associated Press news agency reported.
But she decided to answer questions on Tuesday amid criticism from Republicans and worries from Democratic allies that she was not explaining herself.