Sending rules and list practice
What is double opt-in?
Also called: confirmed opt-in, DOI
Double opt-in requires a new subscriber to confirm their address by clicking a link in a confirmation email before being added to a list. It costs some signups and gives you addresses that are proven real, proven reachable, and wanted by their owner.
Single opt-in adds anyone who types an address into a form, including typos, throwaway addresses and addresses belonging to someone else. Double opt-in filters all three, because only a real mailbox whose owner acted can complete the loop.
It also gives you a record of consent: when and from where each address confirmed. That record is what answers a complaint or a question from your sending platform.
The cost is the people who never open the confirmation. The gain is a list with very few bounces and far fewer complaints, which helps placement for everything you send afterwards.
It is not a substitute for verification. It proves an address worked on the day of signup; data decay starts the next day. Verifying on the form also catches typos before the confirmation email is ever sent.
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By SimpleVerifier Team · Last reviewed 2026-10-13 · All 50 glossary terms