5.x.x permanent failure
SMTP Error Code 551: Meaning, Causes and How to Fix It
SMTP 551 is a permanent failure.
The recipient is not local to this server and no forwarding path is offered. It is permanent, so send to the address the recipient actually uses.
- Class
- 5xx permanent
- Bounce type
- Hard bounce
- Highest severity
- Varies
- Responses on record
- 6
ImprovMX
YandexSMTP 551 responses from email providers
How mailbox providers phrase a 551. Open a provider for the full text, severity and fix for every variation.
ImprovMX5 responses
smtp;551 5.7.1 Due to the very low reputation of the sending domain, this message has been blocked (Code 2).
smtp;551 5.7.1 Loop detected: Email is sent and forwarded from/to improvmx.com. (#id-5.9.0)
Yandex1 response
SMTP 551 questions
›Is SMTP 551 a hard bounce or a soft bounce?
It is a permanent failure, so a hard bounce. The receiving server will not accept the same message on a retry, and the address or the sending problem has to be fixed before you resend.
›What causes an SMTP 551 error?
The recipient is not local to this server and no forwarding path is offered. It is permanent, so send to the address the recipient actually uses. The exact reason varies by receiver, which is why this page lists the specific 551 responses recorded for ImprovMX, Yandex.
›How do I fix an SMTP 551 bounce?
Read the enhanced status code and the message text, not just the number. Wording that names the recipient (user unknown, mailbox unavailable) means correct or remove the address. Wording that names authentication or reputation (SPF, DKIM, DMARC, blocklist) means fix that on the sending side, or clear the listing. Every response on this page has its own guidance.