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Deliverability Letter

552 1

552 Mailbox Not Found

Invalid Recipient

The mailbox referenced in the bounce does not exist at Yahoo.

Hard bounces from invalid accounts should be removed immediately. Continuing to target them damages domain and IP reputation.

Severity

ERROR

Provider

Yahoo Mail

Last Reviewed

2025-06-01

How to Fix 552 1

Follow these steps to resolve this Yahoo Mail SMTP error and restore normal delivery.

  • ✓Drop the address after the first 552 bounce; do not retry.
  • ✓Enable automated bounce handling in your ESP or MTA.
  • ✓Require confirmed opt-in for new Yahoo signups.
  • ✓Audit data entry or import pipelines for formatting mistakes.

Helpful Resources

More Yahoo Mail SMTP Codes

Keep these related troubleshooting guides handy while addressing 552 1.

421 4.7.0 [TS01] – TS01 New or Cold IP Throttle
WARNING
421 4.7.0 [TS02] – TS02 Complaint Rate Deferral
WARNING
421 4.7.0 [TS03] – TS03 Reputation Hold
WARNING
421 4.7.0 [TSS04] – TSS04 Temporary Deferral
WARNING

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