The most popular email apps usher in some sort of innovation: Sparrow had incredible simplicity, Mailbox had snoozes, and Inbox has its intelligent cards and bundles. Their popularity came from changing the way we work with email — so it's easy to overlook today's launch of Airmail for iOS, which has no one standout feature, as just another app. But even though Airmail doesn't have any one standout innovation, it does something that few other mobile apps dare to do: let you do anything you want.

Airmail is shamelessly customizable

Like Airmail for OS X, which has been one of the best Mac email clients for the past few years, Airmail for iOS has an overwhelming number of options. It'll let you do anything you can imagine wanting to do with email — it has snoozes, filters, and third-party app integrations — and probably some things that you'd never even thought of, from setting per inbox notification sounds to bouncing emails and altering Gmail folder mapping. There are more options inside Airmail than in any mobile app I've used in a long time.

Airmail's extensive list of options is something that I suspect most developers would be embarrassed to ship. An app's designer is supposed to know everything, right? They carefully decide where each button goes, how the interface looks, and what options are, and are not needed. In most cases, that's a good thing: too many choices can clutter up an app and make it confusing and unusable. But Airmail manages to tap into a wonderful feeling of customization that, for me at least, comes with a sense of nostalgia for the time I spent downloading alternate gaming skins, installing third-party drivers, and tweaking Windows options in regedit. Customizing an app exactly to your liking can be a lot of fun.

Most things in Airmail can changed to suit your preferences. You can change what happens when you swipe an email, you can enable and disable the appearance of actions like starring and sharing, and you can even reorder multiple core menus. I didn't like that Airmail automatically pulls up inbox filtering options when you start scrolling, so I turned that off. I didn't like the way it showed account icons in its unified inbox view either, so I switched that off and replaced it with a color-coded view.

"With email, [everyone takes] a very, very different approach."

It can feel like Airmail's developers simply couldn't decide on any one direction and chose instead to throw in everything. But Leonardo Chiantini, who co-develops the app with partner Giovanni Simonicca, says Airmail's exhaustive options come by design. "People have different needs," he says. "We think that with email, [everyone takes] a very, very different approach." Airmail is meant to address the needs of professionals who are regularly working in their inbox, he says. "We know we can't be liked by everybody."

Airmail for iOS is now available for $4.99. It works on the iPhone and Apple Watch right now, and Chiantini says an iPad version will come later ("We don't want [an iPad app] that is just a larger iPhone version," he says). Airmail isn't an app that everyone should use. It's big, dense, and occasionally rough around the edges. But those are the same reasons it's easy to love using it. If you have a lot of email to burn through — and you're frustrated that your current app of choice won't let you do work exactly how you want to — Airmail may just be your new best option.