Apple's Mail app for the iPhone might be approximately 2,193% better in iOS6 than it used to be, but it's still a totally mediocre email app. Google ate the one real alternative, Sparrow, and gave us a Gmail app that is pretty decent but only does Gmail. So the state of email on the iPhone is real sad (though not as sad as it is on the desktop). But that's going to change next month, perhaps, with Mailbox, a new email app that looks and feels fresh.
At its core, Mailbox treats email like a to-do list, with the interface drawing more from Twitter and the idea of streams than traditional email clients; composing a new email looks a lot like tweeting, in fact. It relies heavily on clever gestures to get around, like a handful of other iPhone apps — I'd almost call them nouveau touch apps, ones like Clear and the new Twitterific. And it's fast, "blazing fast" even, according to The Verge. In other words, it's approaching email and how we handle it as something that's fundamentally broken and needs to be fixed; this is precisely how the much-beloved Sparrow attacked email and why it was able to make an email app people didn't just use, but liked.
Mailbox will be out sometime after Jan. 1, and I totally suspect it'll be your next email app. Unless you can't get over that icon, anyway, which I'll admit is kind of not very good at all.