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Deliverability Letter

554 5.7.1 [HME1]

HME1 Authentication Failure

Authentication Failure

Apple blocked the message because both SPF and DKIM failed.

Apple expects all production mail to pass SPF and DKIM. When both fail, HME1 is returned immediately and the mail is not retried.

Severity

ERROR

Provider

Apple Mail (iCloud)

Last Reviewed

2025-06-01

How to Fix 554 5.7.1 [HME1]

Follow these steps to resolve this Apple Mail (iCloud) SMTP error and restore normal delivery.

  • ✓Publish accurate SPF records that include every active sending IP.
  • ✓Sign all outbound mail with DKIM using 2048-bit keys and aligned domains.
  • ✓Monitor authentication failures with DMARC aggregate reports.
  • ✓Avoid forwarding mail in a way that breaks the original authentication.

Helpful Resources

More Apple Mail (iCloud) SMTP Codes

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