Post horse is a term used to describe a horse that is used to carry mail or people from one place to another. There are a variety of synonyms that can be used to describe horses that fulfill this role. These synonyms include courier horse, messenger horse, dispatch horse, express horse, and mail horse. Other possible synonyms include pony express horse, stagecoach horse, and carriage horse. Each of these terms is slightly different in meaning, but all refer to a horse that is used to transport people or goods quickly and efficiently. Overall, the term post horse is just one of many ways to describe these important animals.