Email drafting is sneaky and before you say we're just telling people how to do it, I can tell you it's being used by cheating spouses, teenagers, and people breaking the law. It allows for two people to email each other with practically no chance of getting caught.

Here's how it works:

Rather than sending someone an email to their address, the two share an email account such as Gmail. So both people have access to the same account. Instead of sending emails, they write it and save it as a draft.

The next time the other person logs on to check e-mail they'll look for new drafts where they can read the email message and delete it. They'll reply but again, rather than sending it, they'll save the new message as another draft.

Here's why this is impossible to trace: Draft messages don't leave a trail. When one is deleted, it doesn't show up in the trash or deleted folder. It's as if it never existed. The trick can be used on a computer or smartphone. So it can be checked from anywhere in the world.

Six years ago, then CIA director David Petraeus used email drafts to secretly send messages to a woman he was having an affair with. The FBI discovered it while investigating Petraeus. They likely wouldn't have found the messages but some were familiar with the trick because members of Al-Qaeda used it.

The only way to uncover the trick is to check the draft folder for new messages. It's an old trick that has left parents and some investigators scratching their heads.