Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!

Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.

Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.

Bigtent - BigTent is a web-based organization and communication portal for groups.

Mailspring - Mailspring is a mail client for Mac, Windows and Linux.

Nabble - Nabble is a forum software that are embeddable and fully customizable with scripting language.