Courier Deliveries
If you are not in when your parcel arrives, the courier will usually try again, or will leave a card with details on how to pick up your order or rearrange delivery.
Airmail
Airmail packages are delivered by your local post office service and do not require a signature for delivery, so would normally be put through your door or left in the mailbox.
If the package is too large, your local postal delivery service should leave a card with details on how to pick up your order or rearrange delivery.