At one home on my husband’s letter-carrying route, the dog on the other side of the mail slot always barked excitedly and eagerly grabbed the mail. One day the dog’s owner explained that the Labrador had started bringing the mail upstairs to him soon after he got him, so he promptly rewarded with a treat.
After several months there was a slight change in procedure: The dog still delivered the mail upstairs — but only one piece at a time.