SMTP 214 Help Message vs 251 User Not Local
Both SMTP 214 (Help Message) and 251 (User Not Local) belong to the 2xx Positive Completion category. 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. Meanwhile, 251 means that the recipient is not local to the server, but it will forward the message to the specified forwarding address. The server acts as a relay for this recipient.
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 recipient is not local to the server, but it will forward the message to the specified forwarding address. The server acts as a relay for this recipient.
何时出现
When sending to a recipient whose mailbox is hosted on a different server. The current server knows the forwarding address and will relay the message on your behalf.
如何修复
No fix needed — the message will be forwarded automatically. To avoid relaying, send directly to the address provided in the server's response.
主要区别
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 251: The recipient is not local to the server, but it will forward the message to the specified forwarding address. The server acts as a relay for this recipient.
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 251 when when sending to a recipient whose mailbox is hosted on a different server. The current server knows the forwarding address and will relay the message on your behalf.
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 251 (User Not Local): No fix needed — the message will be forwarded automatically. To avoid relaying, send directly to the address provided in the server's response.