That's a question for your local postman. Our usual postman will just leave anything on our door mat if both of our cars are parked outside, or drop it in the Delivery Box otherwise. It all depends on the postman.
If you live in an apartment, they may either just leave a note and ask you to collect it from your local depot, or return it to sender.
If you live in a house, they might deliver it in any way they seem fit - that can be leaving it with your neighbour, leaving it in your letter box, asking you to collect it from your local depot, or returning it to sender. Try to talk to the postman when you get a chance if possible.
If you have an AnPost Delivery Box installed, they will just leave it in the Delivery Box.