What are the pros and cons of SOI?

The primary advantages of single opt-in center on conversion optimization and user experience. By eliminating the confirmation step, SOI maximizes the number of people who complete the signup process-studies suggest that DOI can reduce final subscriber counts by 20-40% due to confirmation email abandonment. SOI also provides immediate gratification, allowing subscribers to receive welcome content or promised incentives without delay. For time-sensitive signups, such as registering for a webinar happening the same day, SOI ensures the subscriber receives necessary information without the risk of a missed confirmation email.

However, SOI carries significant risks that can undermine long-term email program health. Without verification, your list becomes vulnerable to typo addresses (users who mistype their email), spam trap hits (recycled addresses that trigger blacklisting), bot signups (automated form submissions that inflate your list with fake addresses), and malicious subscriptions (competitors or bad actors signing up addresses they don't control). These issues compound over time, degrading deliverability, increasing bounce rates, and potentially leading to blocklisting by ISPs or email providers.

SOI also creates compliance challenges in certain contexts. While it may technically satisfy CAN-SPAM's opt-in requirements, proving consent becomes difficult if a subscriber later claims they never signed up. You uhave only the form submission data, with no verification that the actual email owner completed it. Under GDPR, where consent must be freely given and demonstrable, SOI's lack of verification may complicate your ability to prove valid consent. SOI trades verification for volume-a gamble that pays off only if your signup sources are trustworthy and your list hygiene practices are rigorous.