SMTP 235 Authentication Successful vs 502 Command Not Implemented
SMTP 235 (Authentication Successful) is a 2xx Positive Completion response, while 502 (Command Not Implemented) 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, 502 means that the command is recognized by the SMTP specification but is not implemented on this server. The server understands the command but has chosen not to support it.
Description
The client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session.
Quand vous le voyez
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.
Comment résoudre
No fix needed — authentication succeeded. If you expected this but received a different code, double-check your username, password, and the authentication mechanism.
Description
The command is recognized by the SMTP specification but is not implemented on this server. The server understands the command but has chosen not to support it.
Quand vous le voyez
When using optional SMTP commands like VRFY, EXPN, or TURN that the server administrator has disabled, often for security or anti-spam reasons.
Comment résoudre
Use an alternative approach — for example, if VRFY is disabled, send a test email instead of verifying the address. Check the server's EHLO response for supported extensions.
Différences clés
235 is a 2xx Positive Completion response, while 502 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 502: The command is recognized by the SMTP specification but is not implemented on this server. The server understands the command but has chosen not to support it.
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 502 when when using optional SMTP commands like VRFY, EXPN, or TURN that the server administrator has disabled, often for security or anti-spam reasons.
Quand utiliser lequel
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 502 (Command Not Implemented): Use an alternative approach — for example, if VRFY is disabled, send a test email instead of verifying the address. Check the server's EHLO response for supported extensions.