Yeah this makes no sense, when you called did you tell them that the dog is secured inside the house with the doors closed when he is delivering the mail, and they're still saying that you have to do something?
I mean what kinda issue can there possibly be with the dog inside the house when the mail is being delivered? I mean what, is he doing this to ever house that has a dog in it, that's a lot of houses on his route I'm sure, I'd be very interested to know how many houses he's refusing to deliver to.