This is not terribly important and not worth bothering anybody over, but it came up in a video game I was playing the other day and it's been bothering me ever since: how the heck would one would use biometrics to intercept an outgoing email? (Sent through one of those anonymous disposable email things and employing a firewall and onion router, if it matters in the least.)

Explain like I'm 5, please. (Actually, explain like I know enough about computers to have a Bitcoin wallet but not enough that I'm entirely sure I know how Bitcoin works.)