I haven’t heard exactly how the DOJ obtained the files/emails. It would be interesting to know that. I only see this from DOJ:

These files were collected from five primary sources including the Florida and New York cases against Epstein, the New York case against Maxwell, the New York cases investigating Epstein’s death, the Florida case investigating a former butler of Epstein, Multiple FBI investigations, and the Office of Inspector General investigation into Epstein’s death.