A man was in his front yard mowing grass when his neighbor came out of her house and went straight to the mailbox. The neighbor opened it, looked inside, slammed it shut, and stormed back into her house.
A little later the neighbor came out of the house again, went to the mailbox, again opened it, and slammed it shut again. Angrily, back into the house the neighbor went.
As the man was getting ready to edge the lawn, here came his neighbor again. The neighbor marched to the mailbox, opened it and then slammed it closed harder than ever.
Puzzled by his neighbor's actions, the man asked, "Is something wrong?"
To which the neighbor replied, "There certainly is! My stupid computer keeps telling me I have mail!"