551 5.1.6: Mailbox Has Moved
The 551 5.1.6 bounce means the recipient mailbox has moved or is no longer reachable. Learn how to handle this bounce and update your lists.
Published · Last verified · Maintained by TamingDNS
551
5.1.6
Mailbox Has Moved
Common
🔢 Enhanced Status Code Breakdown: 5.1.6
| Component | Value | Meaning |
|---|---|---|
| Class | 5 | Permanent failure (Hard bounce) |
| Subject | 1 | Address / Destination |
| 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 person has 'moved house.' Their email address has changed, and while the server knows they've moved, it doesn't have a new address to forward your message to. It's like a 'Forwarding Order Expired' notice from the post office.
Common Causes
- The person has a new email address but didn't set up automatic forwarding
- An old forwarding rule has broken or been deleted
- The company has migrated to a new system and some old addresses were left behind
How to Fix This
- Try to find the person's new email address on their website or LinkedIn
- If you have another way to contact them, ask for their updated address
📚 Official Documentation
📋 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
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