Apple introduced privacy protection measures in macOS Monterey and iOS 15 which use a network of randomly assigned IPs to act as proxies when loading (amongst other things) email content. Does anyone know, or know how I can find out, what the network ranges of these services are?
When Apple users allow the settings
Apple currently publishes the IP-address ranges they use (for the purpose of populating Geo-IP databases) on their API here:
https://mask-api.icloud.com/egress-ip-ranges.csv
(Source: https://developer.apple.com/support/prepare-your-network-for-icloud-private-relay)
To prevent users in your network from using Apple's privacy protection proxies Apple does not publish the IP-address ranges in use (as far as I know) and instead they recommend:
and block in your DNS
mask.icloud.com
mask-h2.icloud.com