Home Postcodes by state NSW 2304 Postcode 2304 2304 is the postcode for 7 localities in NSW: Kooragang, Mayfield, Mayfield East, Mayfield North, Mayfield West, Sandgate and 1 more. Localities with postcode 2304KooragangNSWMayfieldNSWMayfield EastNSWMayfield NorthNSWMayfield WestNSWSandgateNSWWarabrookNSW Postcode 2304 State or territory New South Wales (NSW) Localities 7 Council area Newcastle Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 2303 · Postcode 2305