Google Talk
Google announced that a major goal of the Google Talk service is interoperability (which was abandoned around 2013). Google Talk used XMPP to provide real-time extensible messaging and presence events, including offline messaging and voice mailing. Google Talk supported messaging with any service provider that supports the XMPP protocol. This included EarthLink, Gizmo5, Tiscali, NetEase, Chikka, MediaRing, and, according to Google, "thousands of other ISPs, universities, corporations and individual users."