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

Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.

Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.

Drift - A messaging app that helps you grow your business.

Inbox Grader by Freshworks - Free metrics 📈 for your business and team email ✉️

Faqbot - Build your chatbot for FAQ, sales and lead generation automation.