At Knowthis.com, they tested over a 30 day period the sales conversion rates achieved by emailing out to a rented email list against natural search traffic and paid search traffic. The email list significantly outperformed the other marketing channels with a 5.60% conversion rate, followed by natural search at 2.71%. Of course, the quality of the rented list has a major impact on achieving such results or better, but it does show that email marketing is not yet a dead channel despite the level of spam we see today. Just ensure you engage in permission-based marketing practices when engaging in this form of marketing, otherwise it will be considered spamming. You can read more of details of their findings here.