"Cowabee" would have been the name of Mr Sinclair's Station. A station is a large outback stock property/farm.
It wouldn't have been far from Narrandera, as they held the Narrandera mail up earlier that day.
Narrandera is not far from my birth place of Hillston, south western New South Wales. That area was where my Dad spent many of his years as manager of sheep stations. Some places being 30 to 40 thousand acres in size. There are many stations in Australia larger than that where a man can't ride his horse from one end of his land to the other in a single day. It's a hard life in drought time, but one that I know and love. Though the flies and dust can take a hike.