Ship mail is the term used for postal facilities on board ships that are regularly used to carry mail , so-called mail ships , but do not have postal workers on board. The letter-handling, for example, ship's officers , usually the paymaster performed. He has to sell postage stamps en route and hand over the letters posted by the travelers and the crew through the ship's mailbox on the high seas (the mailboxes are closed in foreign ports) in the ports to be called.
- Manual dictionary of the postal system ; 2nd Edition; P. 664
- Frank Arnau : Lexicon of Philately - An Encyclopedia of Postage Stamp Studies . Lingen Verlag Cologne, 1972