It's one of my niggles with e-mail these days: if I type one character wrong in an e-mail address, most systems don't return the message with "Idiot!" messages; they just quietly dump it. Hence I think it's been delivered...
Well you've got our spammer friends to blame for that.
Current best practice, which I agree with 110% is to silently discard emails rather than bouncing back. This is to prevent an effect called "backscatter".