[billswift]

The shipper is the paying customer here, not the person who receives the mail. How would you like it if the post office decided they didn't want to deliver something you mailed out? Or maybe you want them to start collecting money in exchange for not delivering mail? But only some mail - how are they supposed to know which you (and everybody else) want delivered? Can you imagine how expensive keeping a detailed list of what not to deliver to what address would be?