I know of at least one postal delivery person who has been seriously injured by delivering mail to a property where the domestic dog decided to inflict a nasty bite.
Today’s invention is aimed at helping post people make their deliveries in safety.
On approach to a house with a dangerous dog, a postal worker would extract from his bag a telescopic glass fibre fishing rod. This could be extended to reach over a very large yard, as shown.
The rod could simply knock the door and ask for the dog to be chained up, or it could be used (with practice) to slot letters through the letterbox. Parcels could be safely transported onto a front door mat (unless they contain anything edible, obviously).