All orders delivered via Australia Post are done so with safe drop, also known as authority to leave.
This means, your order will be left in a safe place at the delivery address if there is no one there to sign for the delivery. The Australia Post delivery driver determines if there's an appropriate safe, secure and weather-proof spot to leave the parcel. This may sometimes be over your fence, behind a pot plant or in your mailbox.
If Safe Drop isn't suitable, either because of bad weather or other factors, they may choose to take it to a local Australia Post location to be collected. If this happens, you'll be notified by card to let you know where and when you can collect the delivery.