551: user not local
The server does not deliver mail for this recipient and may suggest another address to try. The message was not accepted.
- Standard
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 551
- 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
551 User not local; please try <forward-path>
What it means
RFC 5321 defines 551 for a recipient the server will not deliver to, optionally with a forward-path: another address where the person can be reached. A server may use it when someone has moved and it knows the new address but will not forward. RFC 5321 warns that clients may not update addresses automatically and lets servers disable the feature to avoid revealing information, so 551 with a new address is uncommon. RFC 2034 shows 551 5.7.1 for a server that refuses to forward to remote hosts. It is permanent.
Common causes
- The recipient moved and the server knows the new address but will not forward to it.
- The server refuses to relay mail for a domain it does not handle.
How to fix it
- 01If the reply gives a new address, confirm it with the person and resend there.
- 02Update your records with the new address.
- 03If the text mentions relaying or forwarding, send through your own authenticated outgoing server.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 5.1.6Mailbox 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.
- 550Mailbox unavailable.The receiving server permanently refused the message for this recipient: the mailbox does not exist, cannot be reached, or the server rejected the message by policy.
- 5.7.1Delivery not authorised.The receiving server refuses the message because this sender is not allowed to send to this recipient, as a result of filtering by host or by recipient.
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