CME’s chat client for CME direct uses XMPP they also support connection to other XMPP servers it’s usually mostly server to server or inter domain federation tho (can’t login with just any set of credentials but you can talk to other firms), CME is or at least was interconnected with other financial messenger services like Eikon/Reuters Messenger which is also based on XMPP.

And there are federated networks like the one from Markit

https://www.businesswire.com/news/home/20131007005587/en/Glo...

I don’t think there is a single major financial messenger today that isn’t based on XMPP.