@xssfox And if anyone thinks this is just a problem in the bush, I'll just point you to 3030, the postcode for Werribee and surrounds. As new suburbs have been developed, they started getting allocated new postcodes, but without changing the postcodes of areas which had not been developed. Quandong, at the left, has been cut off from the rest of the postcode, and until 2018 Derrimut (extreme top-right) was part of 3030 as well - it now shares a postcode with neighbouring Laverton North.