Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.
mailcow - An open source mailserver suite.
Bigtent - BigTent is a web-based organization and communication portal for groups.
hMail Server - hMailServer is a free e-mail server for Microsoft Windows.
Nabble - Nabble is a forum software that are embeddable and fully customizable with scripting language.
SmarterMail - SmarterMail is a next generation email management server that is offering several business collaboration and communication features as well.