This is how the music industry does it with material they send out to different parties like reviewers or magazines with tools like Haulix, except they use watermarks that are undetectable to the ear but encoded in the file itself.
Wrt email however, I don't think Paul really minded that it was leaked or just realized it was futile to stop it, perhaps that's why he un-killed it.
Wrt email however, I don't think Paul really minded that it was leaked or just realized it was futile to stop it, perhaps that's why he un-killed it.