In Forrester’s evaluation of email marketing service providers (ESPs), we reviewed 15 vendors against 69 criteria and found that Responsys and ExactTarget are at the front of the Leader pack. All eight Leaders were narrowly separated and achieved Leader status through innovation and a commitment to advancing client education and sophistication. Evaluated vendors include: Acxiom, Alterian, BlueHornet, ClickSquared, Datran Media, e-Dialog, Emailvision, Epsilon, ExactTarget, Experian Marketing Services, Lyris, Responsys, Silverpop, Yesmail, and Zeta Interactive.