Parcels recently delivered by United States Postal Service were stolen from our front porch and also from the front porch of our neighbor. We and our neighbor were home at the time and in both cases our substitute mail carrier did not ring the doorbell.
While reporting the thefts to the post office, I was informed by a supervisor that there is not a policy concerning ringing the doorbell when delivering parcels and the letter carrier can do as he or she chooses.
Our regular letter carrier and UPS for example always ring the doorbell when making deliveries. This should be a no-brainer policy unless the resident has posted instructions to the contrary.