Unlimited Email Tracker - Track opens and clicks, set reminders and delays in Gmail
Battle of the Brands - Compare the online awareness of 2 brands in a battle
Mailtrack.io - The best email tracking solution I've found. Free
Inbox Creature - A super cute virtual pet, delivered right to your inbox.
EmailTrackerPro - EmailTrackerPro is an email tracking and spam filter solution.
Pong Quest - A classic pong quest through unique levels full of twists! Plus 2 player mode!