Sorry frongt, but I think you’re wrongt, haha. I don’t think mailing cash is less private than other methods.

If anyone was concerned enough to the point they were sending cash, they might also take precaution to send coins instead of notes, wearing gloves when handling them, folding their own envelope - do people still lick envelopes anymore? - using lettering stamps instead of handwriting…

Forgive me for the joke on your username, made me laugh.