He is checking his P-Mail

Ed was a successful computer programmer and a happy family man. His life was blessed with a loving wife, 2 kids, three cats and a dog. Ed loved taking Rusty the dog for his evening walk and was proud when his son, little Johnny, began asking to go along on Rusty's evening walks. Little Johnny was an observant and curious child and one evening asked his father: 'Daddy, why does Rusty always sniff that phone pole when we take him for his walk?'Well, Ed wasn't sure how he should answer his son. How DOES one explain the way animals mark their territory to a 6-year-old? Stalling for time Ed asked: 'What do you think he's doing Johnny?' Johnny frowned in concentration, then brightened and said: 'I know! I Know! He's checking his P-Mail!'