Which opt-in method is better for list quality and deliverability?

Double opt-in consistently outperforms single opt-in for both list quality and deliverability metrics. By requiring subscribers to verify their email address through a confirmation click, DOI ensures that every address on your list is valid, reachable, and owned by someone who actively wanted to subscribe. This eliminates the typos, fake addresses, and bot signups that plague SOI lists, resulting in dramatically lower bounce rates and near-zero risk of hitting recycled spam traps from mistyped addresses.

The deliverability benefits of DOI extend beyond just address validity. Confirmed subscribers demonstrate higher engagement rates. They uopen more emails, click more links, and file fewer spam complaints-because they passed through an additional intent barrier. ISPs and mailbox providers use engagement signals to determine inbox placement, so the higher-quality audience from DOI directly translates into better deliverability. Additionally, the cleaner list composition means you're less likely to accumulate the hidden damage from bad addresses that gradually erodes sender reputation over time.

Some marketers resist DOI because they see the 20-40% attrition at the confirmation stage as "lost subscribers," but this framing is misleading. Those non-confirmers include mistyped addresses (who would have bounced anyway), abandoned signups (who likely would have been disengaged), and people who genuinely decided they didn't want your emails (who might have complained instead). The subscribers you "lose" through DOI are largely people who would have hurt your metrics and reputation anyway. DOI doesn't lose good subscribers. It ufilters out the bad ones before they can do damage to your list health and sender reputation.