How does iCloud handle authentication (SPF, DKIM, DMARC)?

iCloud handles authentication (SPF, DKIM, DMARC) consistently with industry standards, requiring proper configuration for reliable delivery. Messages failing authentication face increased scrutiny and potential rejection, particularly as Apple has supported stricter DMARC enforcement.

Apple checks SPF against the sending IP and DKIM signatures against the declared domain. DMARC alignment determines how authentication failures are handled according to your published policy. Apple respects DMARC reject and quarantine policies, filtering or blocking messages that fail authentication per your specifications.

For senders, this means standard authentication best practices apply to iCloud: valid SPF records listing your sending IPs, DKIM signing with proper domain alignment, and DMARC policies appropriate to your authentication confidence level. Apple does not publish extensive postmaster documentation, so following general authentication standards is the best approach.