Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
Coolors.co - The super fast color schemes generator! Create, save and share perfect palettes in seconds!
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Polarite.app - A.I. assisted color scheme generator
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.
Rainglow Color Themes - 320+ color themes for a variety of editors and software.