Bashupload - Upload files from command line to share between servers
Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
FilePizza - Open source application used to transfer file via WebRTC and WebTorrent.
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
BlackHole File Transfer - Blockchain-based file transfer. Designed for everyday use.
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.