5.1.6: mailbox has moved
The address used to be valid, but the mailbox no longer takes mail and the server has no new address to forward the message to.
- Standard
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 5.1.6
- Provider
- Standard SMTP codes
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
5.1.6 Destination mailbox has moved, No forwarding address
What it means
5.1.6 is more specific than 5.1.1: the receiving system remembers that the address existed and says it is closed. RFC 3463 reserves it for permanent failures. It appears when a person has left an organisation or changed provider and the administrators chose to say so plainly. Because the server offers no forwarding address, the only way to reach the person is to get their new address from them. Treat it like any hard bounce and stop mailing the old address. The reply code 551 can carry a suggested new address, when a server is willing to give one.
Common causes
- The person left the company and the mailbox was closed.
- The owner moved to a new address and the old one was retired without forwarding.
- A shared or role mailbox that has been retired.
How to fix it
- 01Remove the address from your lists and mark it as a hard bounce.
- 02Find the person's new address through another channel and update your records.
- 03Recipient admins: if mail should keep reaching the person, set up forwarding or an alias before closing a mailbox.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 5.1.1Mailbox does not exist.The recipient's domain accepts mail, but the mailbox named before the @ does not exist there, so the message was refused and will not be delivered.
- 551User not local.The server does not deliver mail for this recipient and may suggest another address to try. The message was not accepted.
- 5.7.17Mailbox owner has changed.The message asked to be delivered only if the recipient address had the same owner since a given date, and the receiving system says it has changed hands.
Further reading
All 105 standard codesEvery code in the wikiPaste your own bounce