the.com/chain letter

means A letter mailed to several people who are each asked to copy and forward it to more people, often promising luck or threatening misfortune if the chain is broken.

from The term fuses 'chain' — links each tied to the next, unbreakable without cost — with ordinary 'letter.' The format dates to the 1800s, with religious 'letters from heaven' and 'luck letters' promising reward for compliance and ruin for refusal. The name 'chain letter' itself caught on in the early 1900s as these letters spread by post, each recipient forging a new link, and later jumped straight into email and social media without changing its logic one bit.