Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
Salsa - Anonymous messages in your workplace
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Bebop - Bebop provides a nice web interface to a list of publications stored in a BibTeX file.
eM Client - eM Client is a fully-featured email client for Windows and macOS with a clean and easy-to-use interface. eM Client also offers features for calendars, tasks, contacts, notes, and chat.
SicMu Player - SicMu Player is an application that enables users to play audio files on their devices easily.