Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
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.
IrfanView - IrfanView ... one of the most popular viewers worldwide.
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
JPEGView - JPEGView is a small and fast viewer/editor for JPEG, BMP, PNG, GIF and TIFF images.
Geary - Geary is an email application built for GNOME 3.