Kamon.io - Kamon makes an instrumentation library and Application Performance Monitoring tool that helps developers find and fix performance issues in microservices. Works best for Scala (Akka, Play, Lagom) and Java.
GetNotify - GetNotify is a free email tracking software solution.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
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.
Wrike - Wrike is a flexible, scalable, and easy-to-use collaborative work management software that helps high-performance teams organize and accomplish their work. Try it now.
Mailtrack.io - The best email tracking solution I've found. Free