The following articles from Apple's support documentation provide a list of network requirements / ports used by Apple services:
Requests from SimpleMDM come from "a.simplemdm.com". We do not have a specific list or range of IP addresses to whitelist because we use a combination of Google Cloud Platform (GCP) and Cloudflare with dynamic IPs that are subject to change at any time.
If you are whitelisting domains, we do recommend you whitelist the Cloudfare domain "*.r2.cloudflarestorage.com", along with "a.simplemdm.com".
