One of the law enforcement officials said they did not transmit all of their communications as emails from one’s inbox to the other’s inbox. Rather, they composed some emails in a Gmail account and instead of transmitting them, left them in a draft folder or in an electronic ‘‘dropbox.’’ Then the other person could log onto the same account and read the draft emails there. This avoids creating an email trail which is easier to trace. It’s a technique that al-Qaida terrorists began using several years ago and teen-agers in many countries have since adopted.
Associated Press writer Pete Yost contributed to this report.