The perils of letting third party trackers use your CNAME / subdomain.
https://www.simoahava.com/web-development/whats-in-a-cname/
Germany: BW: Guidance on cookies and tracking
Privacymail.info – analyzing trackers in newsletters
is a public, free, research servcie that is analyzing user tracking in the context of newsletters.
Transport for London’s Data Protection Impact Assessment and Privacy Notice for Wifi Tracking
Very interesting , also as it’s public and both, the Data Protection Impact Assessment and the Privacy Notice complement each other.
https://tfl.gov.uk/corporate/privacy-and-cookies/wi-fi-data-collection