Mac: Despite a recent price bump, Airmail is still our favourite email app on Mac, and today it's getting some new features, including to-do list integration, support for El Capitan, and more.
Native support for both Wunderlist and Todoist are easily the nicest features here, because you can now quickly save any messages to your to-do lists. Beyond that, the app's also now fully ready for El Capitan, which includes split screen support and a bit of an interface overhaul. If you're using it on multiple Macs, you'll also be happy to know there's now preference syncing via iCloud, so all your versions work the same. Curiously, there's also now support for Handoff too, which means we're likely getting closer to an iOS release.
Airmail ($12.99) [Mac App Store]