Hi @1982luca - your client name is usually visible after the "@" symbol in the URL when you log on to Experience Cloud instance. e.g.
_domainkey isn't really replaced with anything, but the other values for subdomain.com etc on either side of the CNAME are replaced with your provisioned sending domain. So if your client name is mycompany and your sending domain is e.g. ecomms.mydomain.co.nz then: