SMTP Reply Codes
SMTP 553 — Requested action not taken: mailbox name not allowed
In SMTP Reply Codes, code 553. The official source describes it as “Requested action not taken: mailbox name not allowed”. Its concrete cause depends on the operation and surrounding message.
Code553
Symbol—
Source confidencehigh
Official definition
Requested action not taken: mailbox name not allowed
In plain language
In SMTP Reply Codes, code 553. The official source describes it as “Requested action not taken: mailbox name not allowed”. Its concrete cause depends on the operation and surrounding message.
Context to inspect
- The surrounding operation, version and subsystem determine the actual cause.
- The same numeric value can mean something different in another namespace.
Safe first checks
- Confirm which product, protocol or subsystem produced the code.
- Read the full surrounding error message and inspect relevant logs.
- Compare the code with the linked authoritative documentation before changing configuration.
Important context
Exact wording and enhanced status detail can vary by server; 4xx is generally transient and 5xx permanent. Bare SMTP reply codes are context-dependent; enhanced status codes may provide more detail.