Fixing SPF for iCloud Custom Email Domains
Subscribers to Apple’s iCloud+ have the option of using custom domains with iCloud Mail. You can either purchase a domain through iCloud or bring your own domain. The experience here relates to the bring your own domain option.
Configuring the domain to work with iCloud Mail requires several new domain DNS records. I manage the DNS records for my domain on Netlify. Apple verifies these records before completing the setup.