Unlimited Email Tracker - Track opens and clicks, set reminders and delays in Gmail
PEAR - Connecting newsletters and advertisers 🍐
Newsletter Operating System - All-in-one dashboard to launch & grow your newsletter
Buttondown - Buttondown is the best way to start and run your newsletter
Mailtrack.io - The best email tracking solution I've found. Free
Revue - The easiest way to create and send a curated newsletter