iPhone/iPad: No matter how many filters, labels and other tricks you have set up, organising email is never an easy task. Mail Pilot seeks to make that a bit easier on iOS. While it comes at the high cost of $15.99, it's a robust email app that works with just about any email account.
At its core, Mail Pilot is about organising email in the same way you would organise a to-do list. You can set review dates to deal with email in the future, mark off email's as "complete" or "incomplete", and create contextual lists to organise your email better. Everything works with intuitive gestures, so you're not stuck tapping around the screen a hundred times.
In a lot of ways, Mail Pilot's goals are similar to the previously mentioned Mailbox: it wants to clear out and organise your email as simply as possible. When you mark off an email as "complete", it archives it and gets it out of your face. As for standard email features like compose and reply, Mail Pilot works fine. Oddly though, there doesn't seem to be a way to add an attachment to an email you're composing.
What sets Mail Pilot apart from Mailbox is the fact it supports any IMAP email account. That means Gmail, Yahoo, iCloud, enterprise mail, your personal mail server and plenty more will work with it. It also doesn't run anything off its own servers, so you don't have to worry about privacy issues. That said, Mail Pilot doesn't have push notifications or badges, so if you're looking for an email client that supports push, Mail Pilot won't do you much good.
At $15.99 Mail Pilot is a hard sell, but if you enjoy the system that Mailbox uses but need support for more than just Gmail, Mail Pilot is worth a look.
Mail Pilot ($15.99) [iTunes App Store]