"However, since the Google Talk Service does not support server-to-server encryption via TLS (something that was required by RFC 3920 in 2004), a number of servers (including jabber.org) refuse to establish a connection since May 2014."
https://xmpp.org/2015/03/no-its-not-the-end-of-xmpp-for-goog...
I recall there were issues...]
Wait, what? You could chat from [email protected] on your bespoke xmpp server and send messages to user@gmail without needing a Google account and vice-versa?
Was Google talk really so unpopular that I didn't seriously try to use it until it became the walled garden that didn't support server federation?
For some glorious years between 2006 and 2013 (Hangouts), this was indeed possible. I run my own XMPP server and I used to chat with GTalk users all the time. For literally years.
> They didn't really support federation in a standards compliant way
It was standards compliant enough. In the original RFC, server-to-server TLS was mandatory to implement but not mandatory to enable/deploy. The XMPP community later moved towards enforced server-to-server encryption, but this was many years later and had little impact on GTalk federation during the time that it was supported.
Now I see that Ms allows federation for on-premise lync - but not for office 365. :-(
Everyone wants their own silo, and force their multitude of awful clients on people.
Unfortunately they were the only major service provider to do so, and the capability was later discontinued.