 These are used to assist with the automated sorting of mail that has been addressed by hand for Australian delivery.Postcodes were introduced in Australia in 1967 by the Postmaster-General's Department (PMG) to replace earlier postal sorting systems, such as Melbourne's letter and number codes (e.g., "N3", "E5") and a similar system then used in rural and regional New South Wales.The introduction of the postcodes coincided with the introduction of a large-scale mechanical mail sorting system in Australia, starting with the Sydney GPO.