Extensible Messaging and Presence Protocol

Contact

Can send an administrative message

Accounts

If an account is needed, see Public XMPP Services for that.

This machine is not a public XMPP server, as it would bring it into scope of the public communications regulations, and I have had to lockdown the chat function to get out of scope of Online Safety Act

If using a gmail account, set up standard XMPP clients with app passwords, though these may no longer be able to access federated realms.