Thanks for the additional information. It is helpful. I want to address the outside first and then the front door issue. It sounds to me like he is exhibiting barrier aggression and territorial aggression. He gets worked up while they are still on the other side of the barrier and considers the yard and even the house as HIS and not yours. So part of the solution is to have him see the humans as the boss and that means the yard and house are yours, not his. this is going to mean you being the boss and leader no matter what.
I'm glad he is neutered and that should help. The obedience training is a plus too, but not enough. Going to class is great as it helps teach him to obey even with distractions like other dogs and people. However, to have him see you as the boss, you really need to practice obedience daily at home. Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
This will help reestablish you as the boss and as boss, YOU own the yard. If it is your yard and house, it is your decision who comes in and not the dogs. You will protect the yard not him. So increase the obedience training and start NILF.
Now I also want you to do some training with him. You would do well to have a helper with this part of training. You will have a supply of hot dog slivers in your pocket and have him on a loose leash. Have a person approach the fence. They don't have to get real close, just enough to trigger his reaction. When he react, give a short tug on his leash to get his attention and give a low toned NO as a reprimand. If he stops barking for a second or two, give a treat and have the person walk away. Repeat until he stops reaction, then give a couple of treats and calm praise. Try to end each training session on a positive note. As he stops reacting at a certain distance, have the person get closer until he is no longer reacting. It is a long process but very effective.
It has been found that barrier aggression is often reduced significantly if you can keep the dog off of the barrier. In other words, keep them from getting too close to the fence. While you can train them to stay off the fence, installing an underground fence is a very fast effective way to achieve that. An underground wire buried along the fence line keeps a dog about 3-5 feet from the wire. Petsafe makes a good one and a used one on auction sites is relatively cheap.
You will give the same reprimand any time he barks at someone coming in the yard after you have said they are ok. If he barks after you have said they are ok, then give the same sort of reprimand as I mentioned before and the same rewards if he acts the way you want him to. You might even teach him the quiet command.
It seems easier to teach the quiet command after your dog has learned the speak command. The following site explains teaching speak and quiet commands.
Teaching the speak and quiet command may allow you to have him bark if you know there is someone around that doesn't belong and the quiet will help with controlling his aggression toward visitors.
For the house, you can get a similar barrier device called a scat mat. It keeps dogs away from certain areas. Many owners use them to keep animals off furniture when they are gone or in doorways to keep areas off limits to the dogs. They are great at exits to keep a dog from running out the door and the door aggression. However, teach him to sit and stay at the door until the visitor is seated and then give him a release command and have him lay down in one spot and stay while your visitors are there.
If your classes have not taught a release command, you need to do that. The number one reason a dog breaks a sit or down is no release command is ever given and they have to make the decision on whether they can move or not. So start with a release command training so you can keep him at the door.
When first teaching him to sit at the door when visitors come, you can slip the leash under your foot, have him sit and use the leash to keep him in that spot in a sit or down position as you open the door. Initially he will fight it, but soon will realize it doesn't do any good to try and move away and will stay. When he does that reward him. Have visitors reward him as well.
I hope this information is helpful to you and you are satisfied with my response. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have .