SMTP 235 Authentication Successful vs 551 User Not Local
SMTP 235 (Authentication Successful) is a 2xx Positive Completion response, while 551 (User Not Local) is a 5xx Permanent 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, 551 means that the recipient is not local to this server and the server does not accept mail for forwarding. Unlike 251, this is a rejection — the server will not relay the message.
Mô tả
The client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session.
Khi bạn thấy mã này
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.
Cách khắc phục
No fix needed — authentication succeeded. If you expected this but received a different code, double-check your username, password, and the authentication mechanism.
Mô tả
The recipient is not local to this server and the server does not accept mail for forwarding. Unlike 251, this is a rejection — the server will not relay the message.
Khi bạn thấy mã này
When sending to a recipient that has moved or whose mailbox is hosted elsewhere, and this server refuses to forward the message to the new location.
Cách khắc phục
Check the server's response for a forwarding address and resend directly to that address. Update your contact records if the recipient has permanently moved to a new mail server.
Sự khác biệt chính
235 is a 2xx Positive Completion response, while 551 is a 5xx Permanent 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 551: The recipient is not local to this server and the server does not accept mail for forwarding. Unlike 251, this is a rejection — the server will not relay the message.
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 551 when when sending to a recipient that has moved or whose mailbox is hosted elsewhere, and this server refuses to forward the message to the new location.
Khi nào dùng cái nào
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 551 (User Not Local): Check the server's response for a forwarding address and resend directly to that address. Update your contact records if the recipient has permanently moved to a new mail server.