SMTP 235 Authentication Successful vs 251 User Not Local
Both SMTP 235 (Authentication Successful) and 251 (User Not Local) belong to the 2xx Positive Completion category. 235 indicates that the client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session. Meanwhile, 251 means that the recipient is not local to the server, but it will forward the message to the specified forwarding address. The server acts as a relay for this recipient.
描述
The client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session.
何时出现
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.
如何修复
No fix needed — authentication succeeded. If you expected this but received a different code, double-check your username, password, and the authentication mechanism.
描述
The recipient is not local to the server, but it will forward the message to the specified forwarding address. The server acts as a relay for this recipient.
何时出现
When sending to a recipient whose mailbox is hosted on a different server. The current server knows the forwarding address and will relay the message on your behalf.
如何修复
No fix needed — the message will be forwarded automatically. To avoid relaying, send directly to the address provided in the server's response.
主要区别
SMTP 235: The client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session.
SMTP 251: The recipient is not local to the server, but it will forward the message to the specified forwarding address. The server acts as a relay for this recipient.
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 251 when when sending to a recipient whose mailbox is hosted on a different server. The current server knows the forwarding address and will relay the message on your behalf.
何时使用哪个
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 251 (User Not Local): No fix needed — the message will be forwarded automatically. To avoid relaying, send directly to the address provided in the server's response.