SMTP 250 OK vs 504 Parameter Not Implemented
SMTP 250 (OK) is a 2xx Positive Completion response, while 504 (Parameter Not Implemented) 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, 504 means that a command parameter is not implemented on this server. The command itself is valid but the specific parameter or extension you used is not supported.
Descrição
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.
Quando você o vê
After nearly every successful SMTP command — greeting, specifying sender, adding recipients, or completing message delivery. This is the standard success confirmation.
Como corrigir
No fix needed — the command was accepted. If a command that should succeed returns a different code, check the command syntax and server policies.
Descrição
A command parameter is not implemented on this server. The command itself is valid but the specific parameter or extension you used is not supported.
Quando você o vê
When using SMTP extensions or parameters that the server does not support, such as an unsupported AUTH mechanism or an unrecognized MAIL FROM parameter.
Como corrigir
Check the server's EHLO response for supported extensions and parameters. Use only the mechanisms and parameters listed in the server's capability advertisement.
Diferenças principais
250 is a 2xx Positive Completion response, while 504 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 504: A command parameter is not implemented on this server. The command itself is valid but the specific parameter or extension you used is not supported.
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 504 when when using SMTP extensions or parameters that the server does not support, such as an unsupported AUTH mechanism or an unrecognized MAIL FROM parameter.
Quando usar qual
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 504 (Parameter Not Implemented): Check the server's EHLO response for supported extensions and parameters. Use only the mechanisms and parameters listed in the server's capability advertisement.