How is that different from a mail from a local church asking me to donate, or a local bingo club opening a new location - it's all junk. If I didn't ask for it to be sent to my address, it's all junk.
One person's junk is another person's fuel for heating.
Throughout the year a friend of mine would collect any junk mail, but mostly many copies of the free daily newspapers (Metro, Evening Standard, etc) that litter the trains/underground in the evenings, soak them with water than use a briquette maker to press the paper into blocks. Once dried they provide an ample supply of fuel to heat his home for the 6-10 months of the year (depending on how poorly your home is insulated) that heating is required in the UK.
He definitely didn't have a "No junk mail" sticker on his letterbox.