They may have done things differently on other railroads, but Santa Fe put the baggage car with the Train Baggageman just ahead of the passenger cars.
The Train Baggageman assignment was filled from the Brakeman seniority roster. He also functioned as a Railway Express Agency Messenger until that service ended. He wore work clothes, and his presence in the diner was not appreciated, but it was common for the dinining car crew to carry a meal to him and collect the china and drinkware later. Employees wearing passenger uniforms could eat in the diner, at half price, but not at a table with passengers. Officials could eat in the diner, and the Steward or Waiter in Charge normally "comped" the check.
The Train Baggageman loaded, off-loaded, and sorted the baggage and express, and also the company R.R.B. mail to and from stations. R.R.B. (Railroad Business) mail did not require postage, and the Post Office was not involved, since it was internal communication. Envelopes were typically made of brown paper. Some were sealable, single-use, but most were unsealed with numerous lines printed on the front and back. All had the letters R.R.B. printed on them. They did not have the street address, just the name of the user or office, and the name of the station. When you received Company mail, you scratched out your name and station, and re-used it. Amtrak, as part of its agreement, had to maintain R.R.B. service. but, after personal computers came into use in the 1990's, R.R.B. mail evaporated, as did exchanging paper copies of internal correspondence.
I believe that it was possible to send RRB mail offline when passenger trains of both railroads served the same station (i.e. Chicago, no matter which depot the respective railroads used), however, in practice, it was seldom done, as personal communication (i.e., things other that waybill copies or reports) had to be sent to the Superintendent's Office (via R.R.B mail) for approval. The Superintendent's Office sent it off the Division or offline, if approved.