mailcow is a mail server suite based on Dovecot, Postfix, SOGo, Rspamd and other open source software, that provides a modern Web UI for administration.
A mail service which meets all needs- For individuals: free or Premium (1€/month) Mailo accounts
Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more.
Blue Mind is a complete solution of company messaging, calendars and collaborative work.
TbSync is a central user interface to manage cloud accounts and synchronize their contact, task and calendar information with Thunderbird.
Thexyz build the best tools around for email to make your life simple. Continually updating the product offerings to give customers the very best in email and domain technology.
Servermx is a fast, flexible, and reliable email platform designed for both businesses and individuals. It includes calendar and contact tools that sync to every device.
It provides some unique features such as the email attachment upload in Dropbox.
SMBMail is a groupware server built with a focus on scalability and open standards. It provides secure, enterprise-style email, calendar & collaboration without the high cost.