Home Postcodes by state QLD 4550 Postcode 4550 4550 is the postcode for 2 localities in QLD: Landsborough and Mount Mellum. Localities with postcode 4550LandsboroughQLDMount MellumQLD Postcode 4550 State or territory Queensland (QLD) Localities 2 Council area Sunshine Coast Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 4521 · Postcode 4551