SMTP 250 OK vs 535 Authentication Failed
SMTP 250 (OK) is a 2xx Positive Completion response, while 535 (Authentication Failed) is a 5xx Permanent Negative response. 250 indicates that the requested mail action has been completed successfully. This is the most common positive response in SMTP, returned after HELO/EHLO, MAIL FROM, RCPT TO, and DATA completion. In contrast, 535 means that the authentication credentials provided are invalid. The username, password, or authentication mechanism was rejected by the server.
Descripción
The requested mail action has been completed successfully. This is the most common positive response in SMTP, returned after HELO/EHLO, MAIL FROM, RCPT TO, and DATA completion.
Cuándo lo verás
After nearly every successful SMTP command — greeting, specifying sender, adding recipients, or completing message delivery. This is the standard success confirmation.
Cómo solucionarlo
No fix needed — the command was accepted. If a command that should succeed returns a different code, check the command syntax and server policies.
Descripción
The authentication credentials provided are invalid. The username, password, or authentication mechanism was rejected by the server.
Cuándo lo verás
After submitting incorrect credentials via the AUTH command. The username or password does not match any account on the server.
Cómo solucionarlo
Double-check your username and password. If using an app password (e.g., Gmail, Outlook), ensure it is current and has not been revoked. Also verify the correct SASL mechanism (PLAIN, LOGIN, etc.).
Diferencias clave
250 is a 2xx Positive Completion response, while 535 is a 5xx Permanent Negative response.
SMTP 250: The requested mail action has been completed successfully. This is the most common positive response in SMTP, returned after HELO/EHLO, MAIL FROM, RCPT TO, and DATA completion.
SMTP 535: The authentication credentials provided are invalid. The username, password, or authentication mechanism was rejected by the server.
You encounter 250 when after nearly every successful SMTP command — greeting, specifying sender, adding recipients, or completing message delivery. This is the standard success confirmation.
You encounter 535 when after submitting incorrect credentials via the AUTH command. The username or password does not match any account on the server.
Cuándo usar cada uno
For 250 (OK): No fix needed — the command was accepted. If a command that should succeed returns a different code, check the command syntax and server policies. For 535 (Authentication Failed): Double-check your username and password. If using an app password (e.g., Gmail, Outlook), ensure it is current and has not been revoked. Also verify the correct SASL mechanism (PLAIN, LOGIN, etc.).