ContactMonkey - ContactMonkey tracks email opens and link clicks.
ReadNotify - ReadNotify enables the user to know when email is sent and the reciever reads the email.
GetNotify - GetNotify is a free email tracking software solution.
WhoReadMe - WhoReadMe is an email tracking solution that provides details on read duration, recipient location, organization name, operating system etc.
EmailTrackerPro - EmailTrackerPro is an email tracking and spam filter solution.
Constant Contact - Constant Contact offers email marketing, social media marketing, online survey, event marketing, digital storefronts, and local deals tools.