Here's what I would try.
Have someone approach your door and when he starts barking tell him No and when he complies Click (with a clicker), reward and praise. Continue doing that and you should see him stop quicker each time looking back at you for approval. Within a short period of time he'll learn not barking when he hears someone outside means reward.
You probably will only get a few tries at a time. He'll quickly learn it's a game so you'll want to throw him off. But do it a couple times a day. I bet within a few days you'll see a drastic improvement.
Report back how it goes.
Have someone approach your door and when he starts barking tell him No and when he complies Click (with a clicker), reward and praise. Continue doing that and you should see him stop quicker each time looking back at you for approval. Within a short period of time he'll learn not barking when he hears someone outside means reward.
You probably will only get a few tries at a time. He'll quickly learn it's a game so you'll want to throw him off. But do it a couple times a day. I bet within a few days you'll see a drastic improvement.
Report back how it goes.
