SMTP 235 Authentication Successful vs 451 Local Error
SMTP 235 (Authentication Successful) is a 2xx Positive Completion response, while 451 (Local Error) is a 4xx Transient Negative response. 235 indicates that the client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session. In contrast, 451 means that the requested action was aborted due to a local error in processing. The server encountered an internal issue that prevented it from completing the command.
Descrição
The client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session.
Quando você o vê
After submitting valid credentials via the AUTH command (LOGIN, PLAIN, or other SASL mechanism). The server has verified your identity and you can now send mail.
Como corrigir
No fix needed — authentication succeeded. If you expected this but received a different code, double-check your username, password, and the authentication mechanism.
Descrição
The requested action was aborted due to a local error in processing. The server encountered an internal issue that prevented it from completing the command.
Quando você o vê
When the receiving server hits an internal error such as a database failure, DNS lookup timeout, or anti-spam filter processing error.
Como corrigir
Retry the message later. If you control the server, check its logs for the specific error — common causes include DNS resolution failures, disk I/O errors, or database connectivity issues.
Diferenças principais
235 is a 2xx Positive Completion response, while 451 is a 4xx Transient Negative response.
SMTP 235: The client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session.
SMTP 451: The requested action was aborted due to a local error in processing. The server encountered an internal issue that prevented it from completing the command.
You encounter 235 when after submitting valid credentials via the AUTH command (LOGIN, PLAIN, or other SASL mechanism). The server has verified your identity and you can now send mail.
You encounter 451 when when the receiving server hits an internal error such as a database failure, DNS lookup timeout, or anti-spam filter processing error.
Quando usar qual
For 235 (Authentication Successful): No fix needed — authentication succeeded. If you expected this but received a different code, double-check your username, password, and the authentication mechanism. For 451 (Local Error): Retry the message later. If you control the server, check its logs for the specific error — common causes include DNS resolution failures, disk I/O errors, or database connectivity issues.