551 SMTP bounce: user not local
What 551 means
The server does not handle mail for this user and suggests another path. Mail sent to the suggested address is not guaranteed to be accepted.
Message text
User not local; please try <forward-path> (See Section 3.4)
Common causes of 551
- Recipient domain's MX points to a server that does not host this mailbox
- Old forwarding configuration on the receiving side
How to fix 551
- Run MX lookup on the recipient domain to see which server should receive mail.
- Ask the recipient's administrator to correct the MX or forwarding setup.
Check your domain
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Have the full bounce message? Paste it into the bounce code lookup and it will match the code and the provider for you. Open the bounce code lookup.
How to read 551
The first part, 551, is the SMTP reply code. User not local: the server will not deliver here and suggests another path. Replies that start with 4 are temporary and replies that start with 5 are permanent (RFC 5321 §4.2.1).
This reply carries no enhanced status code. The three-digit reply code is the only machine-readable signal, so read the text that follows it to learn the reason.
Do not keep resending the same message: a permanent failure repeats until the cause is fixed. Correct the cause, then send a new message.
Official source: www.rfc-editor.org. Last verified 2026-10-20.
Related guides
- How to create an SPF record (syntax and examples)
- How DKIM works and how to publish a DKIM record
- How to set up a DMARC record, from p=none to p=reject
Related codes
- 550 SMTP: mailbox unavailable
- 552 SMTP: storage exceeded
- 553 SMTP: mailbox name not allowed
- 554 SMTP: transaction failed
- 5.1.1 SMTP: bad destination mailbox
- 5.1.2 SMTP: bad destination system
FAQ
What does 551 mean?
The server does not handle mail for this user and suggests another path. Mail sent to the suggested address is not guaranteed to be accepted. This is a permanent failure.
How do I fix 551?
Run MX lookup on the recipient domain to see which server should receive mail. Ask the recipient's administrator to correct the MX or forwarding setup.
Is 551 permanent, and should I retry?
551 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.