Synthesio - Synthesio is a social intelligence tool or a marketing software that is specially made for the purpose of social media monitoring and social analytics.

ReadNotify - ReadNotify enables the user to know when email is sent and the reciever reads the email.

Swift Social - All-in-One Social Media Growth and Management Tool

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.

LeadsRX - LeadsRX is a marketing attribution software that gives marketers insights into which advertising campaigns result in conversions.

Mailtrack.io - The best email tracking solution I've found. Free