Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
Mailbird - Mailbird is the best email client for Windows 7, 8 and 10
Roundcube - Web-based IMAP email client
Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
hMail Server - hMailServer is a free e-mail server for Microsoft Windows.
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.