Was it common place for pioneers going west on wagon trains to give mail to Pony Express riders as they passed each other?
In my opinion it is unlikely that a letter would have been carried by a Pony Express rider as he passed by the wagon train. These fellows were on an extremely tight schedule. They had no time to stop. Three of the pockets on the Mochila were locked. The forth pocket was only for the way bill. All mail had to be stamped.