Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Ripple - Ripple connects banks, payment providers, digital asset exchanges and corporates via RippleNet to provide one frictionless experience to send money globally
Groups.io - Email and web based discussion group software, includes archiving, emails, wiki, polls, file...
Cooper - A private professional network for quality intros
Gaggle Mail - Gaggle Mail is a simple and easy to use email list manager.
LinkedIn - LinkedIn is a business-oriented social networking service, mainly used for professional networking.