Disable reachability tests for macOS Server
You can disable Server’s reachability tests.
Reachability testing lets you know if clients for your services can access your server over the Internet.
The Server app securely sends network traffic to serverstatus.apple.com, and asks automated servers at Apple to try connecting to your server (from a 17.x.x.x IP address) for each service that’s enabled. Because Apple servers are outside your local network, they can simulate external clients trying to connect to your server. The results are shown in the Server app.
For details about the tests, see the End User License Agreement (EULA). To find the EULA, click the Server menu, then select About Server. Finally, select License Agreement.
Select your server in the Server app sidebar, then click Overview.
Click Details next to Internet.
Click Disable, then confirm.