FastMail - Email, calendars, and contacts to highest standards of security, privacy and reliability.
Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
Zoho Mail - Zoho Mail is a secure, encrypted, and enterprise-ready email solution, a suite of apps tailor-made for your organization's needs.
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Rackspace Email Hosting - Rackspace Email Hosting is a platform that provides business with web-hosted email services.
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.