Over the course of (almost) seven years of writing for MacStories, I’ve seen email pronounced dead (multiple times), reinvented, redesigned, and, most recently, made smarter with machine learning and cloud services.
I consider myself an email power user (I get approx 2000 emails/day) and there is no way I would try and deal with that many emails on the iPhone or even an iPad.
Call me grumpy, but I’m not willing to re-learn how to use the email client du jour every time the companies that make them either get bought out and closed or go bankrupt. If you want to consider productivity, I’d argue there more email productivity lost in re-tooling every 6 months than there is gained by the tool. I need email to be in a stable client, with a reliable backend, fast sending/receiving, with a consistent and familiar UI. I highly doubt that any indie app is ever going to match the development might that the tech giants can throw at their sunk-cost development of email clients, even Mozilla shuttered Thunderbird because it was dragging down Firefox.