Mailu - Mailu is a simple yet full-featured mail server as a set of Docker images.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Roundcube - Web-based IMAP email client
MailEnable - MailEnable is a Windows based mail server and email server program that is packed with the state of the features and functions like antivirus and spam filtering system, webmail management system, cardDAV, CalDAV and much more.
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.