There comes a time when a dude feels the need to spy on somebody else's mail. It's unethical, it's probably illegal, and it's clearly something you wouldn't want to be caught doing. But hey, we've all been there before. A soon-to-be-ex-girlfriend's fishy correspondence? A letter for your roommate from that fancy company you've always dreamed of working for? Some random dude's mail that you feel like reading, just for kicks?
Obviously you can't go around tearing envelopes open because their intended recipients will know someone went through their mail. What you can do is spritz the envelopes with the X-Ray Spray to check out their contents.