SMTP 235 Authentication Successful vs 554 Transaction Failed
SMTP 235 (Authentication Successful) is a 2xx Positive Completion response, while 554 (Transaction Failed) 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, 554 means that the mail transaction has failed. This is a catch-all permanent error that can occur at any point during the SMTP session, including as a rejection greeting when the server refuses all connections from
Описание
The client has been successfully authenticated using the AUTH command. The server will now accept mail commands from this authenticated session.
Когда вы это видите
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.
Как исправить
No fix needed — authentication succeeded. If you expected this but received a different code, double-check your username, password, and the authentication mechanism.
Описание
The mail transaction has failed. This is a catch-all permanent error that can occur at any point during the SMTP session, including as a rejection greeting when the server refuses all connections from your IP.
Когда вы это видите
When the entire mail transaction is rejected — often due to spam filtering, blacklisted IP addresses, malformed messages, or policy violations detected during the DATA phase.
Как исправить
Check your IP against DNS blacklists (DNSBL) and verify your SPF, DKIM, and DMARC records. Review the full error message for specific rejection reasons. If blacklisted, request delisting from the relevant blocklist.
Ключевые различия
235 is a 2xx Positive Completion response, while 554 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 554: The mail transaction has failed. This is a catch-all permanent error that can occur at any point during the SMTP session, including as a rejection greeting when the server refuses all connections from
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 554 when when the entire mail transaction is rejected — often due to spam filtering, blacklisted IP addresses, malformed messages, or policy violations detected during the DATA phase.
Когда что использовать
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 554 (Transaction Failed): Check your IP against DNS blacklists (DNSBL) and verify your SPF, DKIM, and DMARC records. Review the full error message for specific rejection reasons. If blacklisted, request delisting from the relevant blocklist.