SaneBox ($6 per month) is an amazing email service that makes your existing email inbox more manageable. (I'll describe in more detail how it works in a bit.) A new iPhone app, also simply called SaneBox (for iPhone) is free to download and gives you a new way to view emails that SaneBox has swept out of your inbox and into special folders, where they're less likely to distract you.

When I met recently with Dmitri Leonov, SaneBox's vice president of growth he explained that this new app came about as a result of user demand, rather than a push from within the company itself. (See a five-minute cut of the interview in the video below, and the uncut interview later this month in my weekly Get Organized series.) Many existing SaneBox users will find the app doesn't add much to the core SaneBox experience. But some may prefer a custom app designed specifically for reviewing those less important or unimportant messages. The core SaneBox experience takes place in your existing email account, whether that's Gmail, Outlook, or some other service, so you still get all that SaneBox has to offer if you use the stock Mail app or even Gmail's standalone app.

When you first sign up for SaneBox, it creates one folder by default in your existing email, called @SaneLater. The service looks at all the metadata that your email service preserves, such as whether you've replied to messages from a certain sender, and if so how quickly, or whether you tend to trash certain kinds of messages quickly. It uses that information to make judgment calls about which messages are important (and thus remain in the inbox) and unimportant, in which case they get swept into the @SaneLater folder. You can add more folders, including a "snooze" folder called @SaneTomorrow, that keeps messages out of sight until the next day, when it returns them to your inbox and marks them as unread.

The app shows a list of different SaneBox folders, and a selection for your inbox, but not other folders you may have created in your email program. So for example, my email account has a folder called "2013 TRAVEL," which doesn't even show up in the SaneBox app.

You can review the messages in any of these folders, process messages in bulk (e.g., select a bunch and delete them), or use the app to further "train" SaneBox regarding which messages should remain in the inbox and which ones truly are unimportant.

But here's the thing: You can do all that from the Mail app and the Gmail app already.

The SaneBox app is free to download, and existing SaneBox users may want to check it out just to see if they prefer this interface to their other mobile email apps. But you won't get anything special out of it other than a custom view. If that changes—and I hope it does; I hope the app eventually grows to offer something unique that you can't get from any other app—I'll be sure to let you know with an update to this review.

If you're not a SaneBox user, you should sign up for it immediately, especially if you struggle with email overload and want to be more organized with email. SaneBox is a PCMag Editors' Choice service, and one that I personally recommend to busy professionals.