Mailu - Mailu is a simple yet full-featured mail server as a set of Docker images.
Canary Mail - Privacy-aware email app for Mac & iOS
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
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.
Flow-e - Turn your Gmail or Office365 inbox to a Visual Task Board.