(add Other Providers)
With XMPP account, you can communicate with not just people on XMPP network but also on other networks via Gateways:
If you still have accounts on legacy networks, you can use these Gateways to connect to them:
Credits for this service is here.
I am not the only service provider. You can use XMPP when sign-up for an account at anywhere else if my configuration doesn’t fit your need: