Established in 1999, Return Path is one of the world s leading email service providers. The company s clients include various Fortune 500 firms, online retailers, publishers, market researchers and catalogers from a variety of industries. It provides e-mail delivery monitoring and optimization systems. Return Path s Mailbox Monitor solution has capabilities to cover more than 100 domains worldwide. The company also offers the Sender Score Certified solution, which is a white list accreditation program for permission-based email senders. Additionally, it provides deliverability monitoring tools for internal use and reselling. The company s Return Path Sender Certification Referral Program helps determine deliverability for more than 75 percent of mailboxes operated by the world's leading Internet service providers, including Hotmail, Yahoo and Road Runner.