Not to deliver it, but to take the package or envelope, check the address, then put it in a pile to go to a distribution center in the appropriate, proximal zip code of its destination. That done, the mail might wait up to a day to be flown out, two days at times, then another day to be delivered by ground.
Some breeds of dogs have a natural curl or bend to their tails. But others have been selectively bred to take this curl to an extreme, cork-screw shape. Dog breeds with curly tails referred to as screw tails include Boston Terriers, Pugs, Bulldogs and French Bulldogs.
Similarly to cats, a dog's tail can express a lot of different emotions, from anxiety to relaxation. Doggie tails are rather sophisticated communicators. If your dog's tail is dangling down in a loose manner, it actually may be in its default position, as long as its not hidden between the back legs. When a dog is feeling calm, cool, relaxed and content, he may keep his tail down next to his hind legs and lower thigh area.