Too bad this guy hasn't read the Constitution. Treason has to have two witnesses to the act. Since it was done by computer, unless somebody watched him cut and paste the documents into an email you aren't going to have two witnesses.
Personally, I think you charge him with misuse of government secrets, one count for every page he sent, sentence him to one day for every count, dress him up like Dorothy in the Wizard of Oz and drop him into general population at a maximum security federal prison.
LOL! Not a pretty visual, but...effective.