Ejabberd

From WIKI

Ejabberd- XMPP server software. Ejaberd known to withstand high loads. Ejabbeed used by such large companies as WhatsApp, Facebook, Google, Nintedo.Code server written in Erland.There is a free and paid version of ejabberd. In the paid version, improved technical support. The paid version supports clustering better and has better performance. Ejabberd is a better solution for large servers, but more complicated for administrators. If used PostgreSQL or MariaDb updates are maintained manually.