Home Postcodes by state QLD 4738 Postcode 4738 4738 is the postcode for 2 localities in QLD: Ilbilbie and Koumala. Localities with postcode 4738IlbilbieQLDKoumalaQLD Postcode 4738 State or territory Queensland (QLD) Localities 2 Council area Isaac; Mackay Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 4737 · Postcode 4739