Scan to PDF - Scan, Print, Fax, Download and Store Microsoft Office, PDF and Text Documents and images.
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.
OpenScan - FOSS Document Scanner
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
OrganizerMax - OrganizermaX is an innovative all-new file management app for Mac OS.
Geary - Geary is an email application built for GNOME 3.