1. is more commonly used in british english and in us english. however, british english also uses the noun quite often. the official name of the organisation is the royal mail. the system for sending messages by plane is called and we use the expression for letters, packages etc that go by road, rail or sea. the informal expression is used by people who use e-mail to describe the system of sending letters by a) snail mail. b) mail. c) surface mail. d) postal. e) air mail. f) post. g) ordinary. h) mail.