If you wish to make life as difficult as possible for people delivering things to your door please ensure your letterbox is as close to the ground as possible and has an inner and outer flap separated by an excessively wide gap. Both flaps should have strong springs and there should be a sufficiently dense draft excluder between them to also exclude any post and scour the skin from the hands of the deliverer. For additional points, make sure your house number is unmarked, and the house is placed such that the road that it's on is ambiguous.
I'd suggest keeping a large dog inside to rip the post from the letterbox, but by the time you've managed all the above the point is moot.
(In reality, I don't think any one house managed all of the above. Some did a pretty good job at it though. People buying a house or replacing their front door should try putting a few envelopes though the letterbox to get an appreciation of what they're inflicting on their regular postie, even if they think anybody else delivering things through the post box deserves everything they get.)