FastMail - Email, calendars, and contacts to highest standards of security, privacy and reliability.
Zoho Mail - Zoho Mail is a secure, encrypted, and enterprise-ready email solution, a suite of apps tailor-made for your organization's needs.
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.
163.com - 163.com is an email hosting solution.
Rackspace Email Hosting - Rackspace Email Hosting is a platform that provides business with web-hosted email services.
Microsoft Exchange Server - Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft.