Programs & flows
Double opt-in
Also known as: confirmed opt-in · DOI
A sign-up pattern requiring users to confirm their email address by clicking a link in a verification email before being added to the active marketing list — substantially improves list quality and reduces spam-trap risk.
Double opt-in is a sign-up flow where the user enters their email, receives a confirmation email, and must click a link to complete registration. Unconfirmed addresses sit in limbo and eventually expire. Benefits: filters typos and fake addresses at source, catches malicious sign-ups (where someone submits someone else's email), and produces higher-engagement lists because the confirming action is itself a micro-engagement signal. Drawbacks: 15-30% of sign-ups drop off at the confirmation step, so gross list growth is slower. Required by law in parts of the EU (notably Germany). Worth doing anyway in most other jurisdictions because the list quality difference compounds into deliverability advantage over time. Reconfirmation campaigns (re-asking dormant users to re-opt-in) are the inverse — used to trim a long-neglected list back to active subscribers before escalating a reputation problem.