Two days ago I took a look at CloudMagic's Android email client, and I have to admit, it's a well-designed piece of software. Its blazing fast searching is its claim to fame, but even without this functionality, it's an attractive, holo-friendly app with support for multiple accounts and a unified inbox. But - and for many, this is a big but - the app indexes your mail on CloudMagic's servers. Read More
This post is from a previous deal, but has been updated to reflect the new price!
If you're the corporate type and have had some issues with Android's default Exchange compatibility, then you've probably looked for a good alternative. Among the contenders is an app by NitroDesk called "Exchange By Touchdown," which allows for secure, encrypted Exchange synchronization.
You can only get this deal in the Amazon Appstore. It's still $19.99 in the Android Market!