post-runner
/ˈpəʊs(t)ˌrʌnə/noun
In early use: †a person travelling express, on foot or horseback, with messages, letters, etc.; a courier, messenger (obsolete ). Later: a person who carries the post or mail on foot along a particular route.
Origin
Late 16th century; earliest use found in James Dalrymple (fl. c1596). From post + runner, originally after to run (also ride) the post.