Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
Gaggle Mail - Gaggle Mail is a simple and easy to use email list manager.
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Mail-List.com - Modern Listserv software hosted in the cloud, at affordable rates.
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.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.