Home Postcodes by state SA 5321 Postcode 5321 5321 is the postcode for 2 localities in SA: Cadell and Cadell Lagoon. Localities with postcode 5321CadellSACadell LagoonSA Postcode 5321 State or territory South Australia (SA) Localities 2 Council area Mid Murray Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 5320 · Postcode 5322