I'm creating an email list and my provider ask me if i want to use Double Opt-in or no confirmation. And in the bottom there are those two lines: "We encourage you to choose double opt-in as this list's subscription type. Confirmed subscribers are more beneficial to your business." What they mean? Of course, if they confirm the subscription, it means that they are more "trustable"...but at the end, is there any difference? Please let me know!