Quite a decent email app, i can certainly see myself using this. I have had some issues with contact management though which would make it impractical. The list management features and filters are pretty basic and you can not upload a list of contacts to stop follow ups, you're wholly reliant on them replying to your email so any call to action such as filling a form in on your website would mean they are still continually receiving reminders.

It would probably work if you have a micro list of contacts but there are far better alternative out there.