SMTP 214 Help Message vs 556 Domain Does Not Accept Mail
SMTP 214 (Help Message) is a 2xx Positive Completion response, while 556 (Domain Does Not Accept Mail) 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, 556 means that the destination domain does not accept mail and no forwarding address is available. The domain's DNS configuration (null MX record) explicitly indicates it does not receive email.
Descrição
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.
Quando você o vê
After sending the HELP command to the SMTP server. The response lists available commands or provides usage details for the command you specified.
Como corrigir
No fix needed — this is a normal informational response. Use the provided help text to understand which commands the server supports.
Descrição
The destination domain does not accept mail and no forwarding address is available. The domain's DNS configuration (null MX record) explicitly indicates it does not receive email.
Quando você o vê
When sending to a domain that has published a null MX record (RFC 7505) in DNS, explicitly declaring that it does not accept any email messages.
Como corrigir
Verify the domain's MX records — a null MX (priority 0, empty host) means the domain intentionally rejects all mail. Contact the recipient through an alternative channel.
Diferenças principais
214 is a 2xx Positive Completion response, while 556 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 556: The destination domain does not accept mail and no forwarding address is available. The domain's DNS configuration (null MX record) explicitly indicates it does not receive email.
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 556 when when sending to a domain that has published a null MX record (RFC 7505) in DNS, explicitly declaring that it does not accept any email messages.
Quando usar qual
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 556 (Domain Does Not Accept Mail): Verify the domain's MX records — a null MX (priority 0, empty host) means the domain intentionally rejects all mail. Contact the recipient through an alternative channel.