SMTP 214 Help Message vs 450 Mailbox Unavailable
SMTP 214 (Help Message) is a 2xx Positive Completion response, while 450 (Mailbox Unavailable) 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, 450 means that the requested mail action was not taken because the mailbox is temporarily unavailable. This could be due to the mailbox being locked by another process or a temporary policy restriction.
説明
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.
このコードが表示される場合
After sending the HELP command to the SMTP server. The response lists available commands or provides usage details for the command you specified.
解決方法
No fix needed — this is a normal informational response. Use the provided help text to understand which commands the server supports.
説明
The requested mail action was not taken because the mailbox is temporarily unavailable. This could be due to the mailbox being locked by another process or a temporary policy restriction.
このコードが表示される場合
When the recipient's mailbox exists but is currently locked, busy, or subject to greylisting. The server is asking you to try again later.
解決方法
Retry delivery after a few minutes. If using greylisting, the second attempt will typically succeed. For persistent failures, check if the recipient's mailbox is full or disabled.
主な違い
214 is a 2xx Positive Completion response, while 450 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 450: The requested mail action was not taken because the mailbox is temporarily unavailable. This could be due to the mailbox being locked by another process or a temporary policy restriction.
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 450 when when the recipient's mailbox exists but is currently locked, busy, or subject to greylisting. The server is asking you to try again later.
どちらをいつ使うか
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 450 (Mailbox Unavailable): Retry delivery after a few minutes. If using greylisting, the second attempt will typically succeed. For persistent failures, check if the recipient's mailbox is full or disabled.