Messages service can let your chat server communicate with other servers using Messages service, allowing buddies from other servers besides your own. Server-to-server chat communication is called federation. If you want to control which servers can be federated with your own, see Enable server-to-server federation.
To establish communication between servers on different networks, administrators must configure domain name server (DNS), network address translation (NAT), and firewalls, as needed.
Select Messages in the Server app sidebar.
Select “Enable server-to-server federation.”
If this is the first time you enabled federation, a configuration page appears. Otherwise, click Edit to see the configuration pane.
Select Edit to restrict federated domains, as needed.
Only host names and domains that are listed can communicate with your server. This is called a federation domain list.
The federation domain list entries can be complete host names or domains. (This can be a mix of servers and domains.)
The server software does the rule-matching to see if these domains can interact. Any domain or host not in the approved list cannot communicate with your Messages server.
If you’ve restricted federated domains, select “Require secure server-to-server federation” to restrict communication to SSL-encrypted connections.
Secure federation requires the federated server to accept SSL-encrypted connections. You can change which SSL certificate is used for encryption by using the certificate management feature of the Server app. For more information, see Use an SSL certificate.