Dynamically Personalized Emails by QGraph - Hyper-personalized emails for E-commerce
Mailtrack.io - The best email tracking solution I've found. Free
Nova Inbox - Personalize emails in seconds, right from your inbox
ReadNotify - ReadNotify enables the user to know when email is sent and the reciever reads the email.
InboxSDK - First usable API to write Gmail Apps for 1B active users
Bananatag - Find out what happens to your emails after you press send! Add email tracking, attachment tracking, email scheduling and templates to your daily emails.