“I usually don’t recommend single opt-in email captures. Double opt-in provides an extra measure of security, even if it means a slightly reduced mailing list size.”

@neilpatel

If you use a single opt-in form for your email lists, you’ll want to make sure that you give your visitor a warm welcome message immediately after he or she gives you an email address. You can use a double opt-in form to garner a leaner, and much more interested, list by telling users to check their email to confirm subscription.