SMTP 214 Help Message vs 421 Service Not Available
SMTP 214 (Help Message) is a 2xx Positive Completion response, while 421 (Service Not Available) is a 4xx Transient 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, 421 means that the SMTP service is not available and the server is closing the transmission channel. This may be sent as a greeting or during a session if the server needs to shut down.
Mô tả
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.
Khi bạn thấy mã này
After sending the HELP command to the SMTP server. The response lists available commands or provides usage details for the command you specified.
Cách khắc phục
No fix needed — this is a normal informational response. Use the provided help text to understand which commands the server supports.
Mô tả
The SMTP service is not available and the server is closing the transmission channel. This may be sent as a greeting or during a session if the server needs to shut down.
Khi bạn thấy mã này
When connecting to a mail server that is overloaded, undergoing maintenance, or shutting down. The server cannot handle your request right now.
Cách khắc phục
Retry the connection after a delay. If the issue persists, check server status and resources (CPU, memory, disk). Rate limiting or greylisting may also trigger this response.
Sự khác biệt chính
214 is a 2xx Positive Completion response, while 421 is a 4xx Transient 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 421: The SMTP service is not available and the server is closing the transmission channel. This may be sent as a greeting or during a session if the server needs to shut down.
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 421 when when connecting to a mail server that is overloaded, undergoing maintenance, or shutting down. The server cannot handle your request right now.
Khi nào dùng cái nào
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 421 (Service Not Available): Retry the connection after a delay. If the issue persists, check server status and resources (CPU, memory, disk). Rate limiting or greylisting may also trigger this response.