Powerful plugin that takes your WordPress.org powered site beyond the blog with social-network features like user profiles, activity streams, user groups, and more.

GPL-2.0

PHP

Elgg

Powerful open source social networking engine.

GPL-2.0

PHP

SquirrelMail

Another browser-based IMAP client.

GPL-2.0

PHP

b1gMail

Complete email solution that runs on any webspace with PHP and MariaDB. It supports POP3 catchall mailboxes and can also integrate with Postfix or b1gMailServer if you're running your own server.

GPL-2.0

PHP

phpBB

Flat-forum bulletin board software solution that can be used to stay in touch with a group of people or can power your entire website.

GPL-2.0

PHP

AnonAddy

Email forwarding service for creating aliases.

MIT

PHP