NAPS2 - NAPS2 is a document scanning application with a focus on simplicity and ease of use.
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
Simple Scan - Project information. Part of: The Gnome Project. Maintainer: Simple Scan Development Team. Driver: Simple Scan Development Team. Licence: GNU GPL v3.
Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
XSane - A good proposal for SANE-2 has been written.
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.