Related Clues:

• Bills in a box
• Large number have a complaint when it goes astray
• Armour; posted items
• There are more than four letters in this
• First-class stuff
• Posted bills, e.g
• Form of armour; post
• Ordinary 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