I am sure this has been done to death, but the search function isn't working, and neither is my trawling through past threads.
I have a Bull Arab called Blossom, who is 2 years old. She barks at strangers when the come to the door or walk past our property.
She was a rescue dog who had been badly abused, and as such, is often scared. This has been reducing since she has been with us, but I have a feeling it is related. If an adult she is not vey familiar with (me, DH or my parents) comes to the door, or even walks past the property she will growl or bark until we let the person inside. While she is scared of some people, she retreats rather than growls or barks once they are inside. If she feels cornered by a stranger inside (which we try to prevent, she will whine, but not show signs of aggression.
Any other time, she is very well behaved, she walks well on lead, and is friendly and sociable to other people and dogs on walks and at the dog park. We have a toddler, and she is extremely patient around any child. She NEVER shows aggression to children irrespective of what they are doing, including running round screaming and trying to climb on her back (which we actively prevent).
What can we do to reduce this incidence? As she is a big dog she tends to freak out the postie and Pizza guys.