Hi lynda,
What breed is your dog?
Some dogs are bred to bark at strangers and some dogs don't even bark when a robber comes in the house so it is important to know what breed or breed mix your dog is.
Is her barking starting with a growl, or just a bark when she sees the mailman on the street? Is her tail tucked in between her hind legs, or is she wagging her tail, or sticking it up high?
Barking has a lot of different meanings for dogs so observe her body gesture and let us know more on it.
However, when you want to correct an unfavorable behavior, you can either ignore or reprimand or give her a command that can totally conflict what she is doing. For example, when she starts barking at home, call her away from the door or window and make her Sit and Stay. If she does, praise and treat her. One of my dogs is a very guard dog but she starts barking even when our neighbor across the street takes the garbage out. I am having a hard time teaching her to stop barking myself.
Good luck