The tail position shows the mood of a dog and a place it takes in a hierarchy. It should be noted that, with some breeds, a tail in neutral position is practically set on its back. There are variations since some breeds have curled tail on the back which makes the shape even less noticeable, like in Tibetan Spaniel, Pekingese, Lhasa Apso, Chow Chow, spitzes...
Certain domestic dog breeds, even when they are not displaying dominance or confidence, have an up high tail. This is common with: Beagle, Airedale Terrier, Fox Terrier, West Highland White Terrier (commonly known as Westie) and many other breeds.
On the other hand, there are sighthounds such as Greyhound, Italian Greyhound... with tail set between its legs.
There are also tailless breeds or breeds that are natural bobtails, like English Bulldog, French Bulldog... while some are completely or partially tailless due to tail docking procedure: Doberman Pinscher, Boxer, Rottweiler, Cane Corso... In both cases it is difficult to determine whether the tail is set up high, if it is horizontal or down.
In these situations it is difficult to understand what the tail is communicating because the position and the shape that is demanded in certain breeds is stimulated by human "aesthetic" values and dog show criteria, when those types of tails send mixed signals to other dogs as well as to humans.