For a while our mail man was a friend from HS that was in band. When I found out it was a friend would let him in the house and get him something to drink and/or maybe use the restroom. Penny, my first golden would open the door, and sometimes would open the door and wait for him to come around the garage to meet him.
When his route changed she ran out to meet him and was surprised by the new carrier coming around the corner of the garage kicking and hitting her with the letter bag. I saw it an Penny was sitting on her wagging tail with a big golden retriever smile when the new carrier started kicking. Opened the door and she quickly ran into the house. Never once growled or barked at him.
I told him the last carrier was a HS friend the she liked him he always pet her and came in for a cool drink or to use the facilities. And as far as I was concerned he had no business being a mail carrier. And to just remember if he is thirsty or needs to use the facilities to please not knock on our door. And if my dog sees him try to relieve himselt anywhere near this house or yard my dog can easily open the door, run out, and bite him. And I might just let her.
After that incident, every time that mail man came by she would bark at him from behind out screen door. She never opened it. When his route got changed Pepper didn't bark at the next carrier and he told me about my friend telling about my friendly dog (so that other carrier knew and was an arse). Told new carrier he was welcome and only had to knock and I or the dog let him in to a cool drink or use our facilities. Within a week Pepper was going out and meeting him as he rounded the garage.
Penny was such a smart good dog!