I’ve never used Newton Mail, but according to the app’s description, it appears to offer plenty of useful features. For example, it offers read receipts, Send Later, plus a Recap feature. It also has familiar features like Snooze and Undo Send.
For me, the issue is the $49.99/year price tag for an email app. I understand that people may swear by this app and the amount of productivity it allows for, but considering Inbox was free, and Gmail will probably always be free, it’s hard to dive into the world of paid email services.
For you Newton lovers, follow the link below to get yourself setup. If you’re curious about the service, you can signup to receive two free weeks of Newton.