Mailspring - Mailspring is a mail client for Mac, Windows and Linux.

Scanbot - Scanbot is a mobile app that allows you to use your device's camera as a document scanner. The app is capable of scanning a large number of source materials, and it can handle QR codes as well.

Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!

Scanner Pro - Scanner Pro turns your iPhone into portable scanner in your pocket.

The Bat - The Bat! is a secure desktop email client for Windows, designed to protect your correspondence against third-parties and to save your time.

Genius Scan - On The Go.