SMTP code 455 is used to indicate a temporary issue with the server, where
it suggests retrying the request at a later time. This code usually implies
a transient condition which is expected to be resolved after some delay.
Each digit in an SMTP response code carries a specific meaning.
Transient Negative
A temporary condition prevented completion. The sender should retry.
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.
455 4.4.5 Try again later
Why you might receive this response.
To address a 455 error:
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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