What is a double opt-in?
Also called: confirmed opt-in
Double opt-in requires a subscriber to confirm their address by clicking a link in a confirmation email before being added to a list. It costs you some signups and buys a list of addresses that are provably real, provably reachable, and provably wanted by their owner.
Single opt-in adds anyone who types an address into a form, including typos, throwaway addresses and addresses belonging to other people. Double opt-in filters all three, because only a real mailbox whose owner acted can complete the loop.
The cost is real: expect to lose a meaningful share of signups to people who never open the confirmation. What you gain is a list with a near-zero bounce rate and far fewer complaints, which compounds into better inbox placement for everything you send afterwards.
It is not a substitute for verification. Double opt-in protects the point of collection; addresses still decay at roughly 2% a month afterwards as people change jobs and close accounts.
Last reviewed 2026-09-11