Spark will work with any IMAP email server, and starting today it is offered for all Apple iPad models ranging from the 7.9-inch Apple iPad mini 4 to the 12.9-inch Apple iPad Pro. The iPad version of Spark optimizes the UI to fit the larger screens on a tablet. And with the update, Spark is also compatible with the Apple Watch and WatchOS 2. The app now supports English, German, Chinese, Russian, Spanish, French, Italian, Japanese, and Portuguese.
To install Spark on your iOS device, click on the sourcelink. Your iOS device must be running on iOS 8.3 or later. We should also point out that Spark is a free download from the App Store.
source: Spark via MacRumors