Related Clues:

• First-class stuff
• Form of armour; post
• Armour that could be first class
• Type of armour
• Smartphone filler
• Fan letters
• Old school fan letters
• Post to a box
• It might be junk
• Pigeonhole filler
• Suit of armour
• Pony Express concern
• Bills, catalogs, etc
• Six-day-a-week delivery
• Much of it is junk