SMTP 450 Mailbox Unavailable vs 455 Server Unable to Accommodate
Both SMTP 450 (Mailbox Unavailable) and 455 (Server Unable to Accommodate) belong to the 4xx Transient Negative category. 450 indicates 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. Meanwhile, 455 means that the server is currently unable to accommodate the requested parameters. This is a general temporary failure indicating the server cannot process the specific request at this time.
Descripción
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.
Cuándo lo verás
When the recipient's mailbox exists but is currently locked, busy, or subject to greylisting. The server is asking you to try again later.
Cómo solucionarlo
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.
Descripción
The server is currently unable to accommodate the requested parameters. This is a general temporary failure indicating the server cannot process the specific request at this time.
Cuándo lo verás
When the server temporarily cannot handle a specific aspect of your request, such as a particular extension or parameter that requires resources not currently available.
Cómo solucionarlo
Retry the command later or try with different parameters. If the error persists, simplify the request or contact the server administrator to check resource availability.
Diferencias clave
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.
SMTP 455: The server is currently unable to accommodate the requested parameters. This is a general temporary failure indicating the server cannot process the specific request at this time.
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.
You encounter 455 when when the server temporarily cannot handle a specific aspect of your request, such as a particular extension or parameter that requires resources not currently available.
Cuándo usar cada uno
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. For 455 (Server Unable to Accommodate): Retry the command later or try with different parameters. If the error persists, simplify the request or contact the server administrator to check resource availability.