ESRI suggest API returning incorrect result for Australian postal code.

Question

In one of our applications, we use ESRI suggest API to get suggestions against postal codes. However, we are getting incorrect responses for Australian postcodes. 
example we tried with postcode `3068`

we got suggestions like

"3068, Clifton Hill, Northcote, Melbourne, Victoria, AUS"
 "3068, Brunswick East, Fitzroy North, Melbourne, Victoria, AUS"

which is incorrect.

GrahamWood-HWC · Answer

here is the definitive source for Australian postcodes
https://auspost.com.au/postcode

3068 is Valid for both suburbs..

post codes in Australia have their history in the catchment area of a post office(back in the days of post) which may reach beyond suburb boundaries... my post code reaches across 9 suburbs

SHIVAM1995 · Answer

API used was
https://geocode.arcgis.com/arcgis/rest/services/World/GeocodeServer/suggest?text=3068 &f=json&token=xyz&outFields=*&maxSuggestions=15&category=Address,Postal&countryCode=AU&returnCollections=true