Pleroma : Pleroma is a federated social networking platform, compatible with GNU social and other OStatus implementations. It is free software licensed under th...
Postal : Postal is a complete and fully featured mail server for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready f...
Radicale : The Radicale Project is a complete CalDAV (calendar) and CardDAV (contact) server solution.
GNU social : GNU social is a continuation of the StatusNet project. It is social communication software for both public and private communications. It is widely su...
Prisma : Prisma turns your database into a powerful GraphQL API which you can either use to build your own GraphQL server or connect to it directly from the fr...
Social server with an ActivityStreams API. It's a stream server that does most of what people really want from a social network.