My hubby is a mailman too!!! We don't have the same problem, tho. Bailey loves, loves, loves everyone!!!
I watched an episode of Its Me or the Dog - Victoria Stillwell. The Poodle absolutely hated the man of the house. It would growl whenever the man was close. The poodle was very protective of the the wife and daughter. Victoria trains with treats. Her method was to give the man treats and let the dog know that he had the treats. If the dog got close to the man without growling it got a treat. The dog soon associated being with the man as positive experience.
On the same episode - the dog couldn't be in bed with the wife and husband without growling at the man. So, Victoria put the wife and dog in the bed together - and told the husband to enter the room and approach the bed. If the dog growled at the husband, then the dog was immediately put on the floor. This was repeated over and over and over again - until the dog realized it could only stay on the bed if it didn't growl. I guess you could say that staying on the bed was the "treat" for the poodle - who obviously wanted to be there.
Between the two training exercises, the dog started to come around.
I hope your situation isn't as extreme as this family's situation - but I thought the training techniques in this show were positive and had good results.
Good luck
