SMTP 214 Help Message vs 501 Syntax Error in Parameters
SMTP 214 (Help Message) is a 2xx Positive Completion response, while 501 (Syntax Error in Parameters) is a 5xx Permanent Negative response. 214 indicates that a help message response containing information about the server's supported commands or a specific command's usage. This is a human-readable reply to the HELP command. In contrast, 501 means that the command was recognized but the parameters or arguments are syntactically invalid. The server understood what you wanted to do but could not parse the details.
描述
A help message response containing information about the server's supported commands or a specific command's usage. This is a human-readable reply to the HELP command.
何时出现
After sending the HELP command to the SMTP server. The response lists available commands or provides usage details for the command you specified.
如何修复
No fix needed — this is a normal informational response. Use the provided help text to understand which commands the server supports.
描述
The command was recognized but the parameters or arguments are syntactically invalid. The server understood what you wanted to do but could not parse the details.
何时出现
When a command like MAIL FROM or RCPT TO has a malformed email address, missing angle brackets, or invalid characters in the arguments.
如何修复
Review the parameter format — email addresses should be enclosed in angle brackets (e.g., <[email protected]>). Check for stray spaces, missing colons, or encoding issues.
主要区别
214 is a 2xx Positive Completion response, while 501 is a 5xx Permanent Negative response.
SMTP 214: A help message response containing information about the server's supported commands or a specific command's usage. This is a human-readable reply to the HELP command.
SMTP 501: The command was recognized but the parameters or arguments are syntactically invalid. The server understood what you wanted to do but could not parse the details.
You encounter 214 when after sending the HELP command to the SMTP server. The response lists available commands or provides usage details for the command you specified.
You encounter 501 when when a command like MAIL FROM or RCPT TO has a malformed email address, missing angle brackets, or invalid characters in the arguments.
何时使用哪个
For 214 (Help Message): No fix needed — this is a normal informational response. Use the provided help text to understand which commands the server supports. For 501 (Syntax Error in Parameters): Review the parameter format — email addresses should be enclosed in angle brackets (e.g., <[email protected]>). Check for stray spaces, missing colons, or encoding issues.