SMTP code 553 is used to indicate a rejection due to the recipient's
email address being invalid, typically in scenarios where the address
is not recognized by the recipient's mail server. This can occur due to
misspelled email addresses or when the email address does not exist on
the receiving server.
This error message often refers to the domain within the email address but
this may not always be the case.
Each digit in an SMTP response code carries a specific meaning.
Permanent Negative
The command failed permanently. Do not retry without changes.
Mail System
Status of the mail system as a whole.
Specific Condition
The third digit narrows the response. Zero is typically generic; higher values are increasingly specific.
Typical server responses you may encounter.
553 5.3.0 <[recipient email]>... User unknown, not local address
553 5.1.2 We weren't able to find the recipient domain. Please check for any spelling errors, and make sure you didn't enter any spaces, periods, or other punctuation after the recipient's email address.
Why you might receive this response.
To address a 553 error:
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CloudMailin can help troubleshoot and resolve SMTP issues.
SMTP code 421 indicates a temporary issue with the server that prevents it from processing requests
SMTP code 450 is a generic temporary error and is used in a wide variety of conditions by the receiving server
SMTP code 451 indicates a temporary local error on the receiving server
SMTP code 452 is used to indicate that the recipient's email server is unable to accept the message due to a lack of storage space, too many recipients, or insufficient system resources
SMTP code 454 indicates an authentication issue, typically suggesting that the server is denying relay access due to a lack of proper authentication from the sender
SMTP code 455 is used to indicate a temporary issue with the server, where it suggests retrying the request at a later time
SMTP code 530 typically indicates that authentication is required to proceed with the requested email operation
SMTP code 550 is a permanent failure notice, typically indicating that the recipient's email address is invalid or unavailable
SMTP code 552 generally indicates a failure due to storage issues or a limit imposed by the recipient's mail server
SMTP code 553 is used to indicate a rejection due to the recipient's email address being invalid, typically in scenarios where the address is not recognized by the recipient's mail server
SMTP code 554 is a permanent failure notice, indicating that the message has been rejected and will not be delivered