I would like to suggest a simple rule for writers: NEVER buy email addresses to promote your book.
Last week, I discovered an online outlet offering to sell lists containing the email addresses of over 15,000 HubPages members and more than 20,000 Amazon forum members so writers can spam unsuspecting readers. The outlet offered to sell these addresses for $15 and $20 respectively.
As someone who receives hundreds of unsolicited emails every week, I will not link to this site and I STRONGLY advise aspiring writers not to use these services. The only way to find new readers is to earn them honestly through social network outreach, author readings, online writing and other conventional promotional routes.