To opt for Australia Post Fulfillment, your volumes need to be at least 1500 parcels a month. You must align with Australia Post network specs and should not be shipping temperature-controlled, perishable, or hazardous goods. You also need to satisfy their weight and volumetric requirements - the weight of packages should not exceed 22 kg, they should not be longer than 105 cm, and the volume should not exceed 0.25 cubic meters.