Knowledgebase

SMTP 5xx Error codes

500 - The server could not recognize the command due to a syntax error.
501 - A syntax error was encountered in command arguments.
502 - This command is not implemented.
503 - The server has encountered a bad sequence of commands.
504 - A command parameter is not implemented.
550 - The requested command failed because the user's mailbox was unavailable (for example because it was not found, or because the command was rejected for policy reasons).
551 - The recipient is not local to the server. The server then gives a forward address to try.
552 - The action was aborted due to exceeded storage allocation.
553 - The command was aborted because the mailbox name is invalid.
554 - The transaction failed. Blame it on the weather.

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