Like many fast ships on the North Atlantic, the Titanic was licensed to carry both United States and Royal Mail, hence the designation RMS (Royal Mail Ship) by an agreement between the Oceanic Steam Navigation company, the parent company of the White Star Line, and Her Majesty's Postmaster General.

Hidden from passengers, the Ship carried letter sorting and storage rooms far below on Lower and Orlop Decks.  In these rooms, government postal workers (three Americans and two British) opened hundereds of bags of mail destined for delivery in the United States and Canada.  Letters and parcels were examined by hand and then placed in an enormous pigeonhole cabinet, with each box representing the intended city of delivery. This sorting at sea expedited the mail's delivery once it reached land.

The degree of safekeeping for letters and parcels depended on the type of insurance purchased by the sender.  Ordinary mails were dispatched in mailbags kept in common compartments; but insured or registered mail was kept sequestered in its own storage room.  A special strong room, called a specie room, was provided if the Titanic were called upon to carry gold or currency.  This room was under the purser's domain.

For more in-depth information on Titanic's Post Office, please visit "Posted Aboard RMS Titanic".