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Bounce Decoder: 551 5.1.6

SPF, DKIM, DMARC, FCrDNS, Blacklists & Inbox Prediction

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551 5.1.6 — Mailbox Has Moved

The 551 5.1.6 bounce means the recipient mailbox has moved or is no longer reachable at this address. Learn what to do.

🔴
Permanent Failure (Hard Bounce)
SMTP Code
551
Enhanced Code
5.1.6
Category
Mailbox Has Moved
Frequency
Common

🔢 Enhanced Status Code Breakdown: 5.1.6

Component Value Meaning
Class 5 Permanent failure
Subject 1 Addressing
Detail 6 Mailbox Has Moved

Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.

💬 What This Error Means

This email address has been moved or migrated, but the forwarding configuration is missing or broken.

Common Causes

  • The recipient migrated to a new email address without setting up forwarding
  • A forwarding loop was detected by the server
  • The forwarding destination no longer exists

How to Fix This

  • Contact the recipient through another channel to get their current address
  • Update your records with their new email address

📋 Real-World Example Messages

These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis. 

551 5.1.6 User not local; please try <[email protected]>

🔗 Related Error Codes

550 5.1.1
Mailbox Does Not Exist
501 5.1.8
Bad Sender Address

📚 Official Documentation

↗ RFC 5321 — SMTP
🔍

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