"Don't blame the dog blame the owner" is something my sister reads and hears constantly but 90 percent of all dogs do nearly same thing regardless of owner. That being said there are better owners who do try to keep mail carriers as safe as possible and we have zero respect for those that don't and go "he's not gonna bite" or whatever.
I dont have too much trust in dogs myself after having bitten by one twice (first time seriously bled me and I had to be admitted to urgent care and take medication and get a tenatus shot), the same one who I thought knew me for a while and I agreed to dogsit thru walking and tried to feed.