Common SMTP Error Codes
Mar 13, 2006 03:25 PM
The following are some common SMTP status codes. Sometimes these errors are immediate, for example an error that pops up in Microsoft Outlook, while other times the error shows inside of an email error receipt sent by a server.
Tip: When the error begins with a 4, example 451, the error message is temporary; most email servers will retry delivery for a predetermined amount of time. Error messages beginning with the number 5, example 551, are permanent errors that cannot be resolved by the server and the message will not be retried.
421 Service not available, closing transmission channel (This may be a reply to any command if the service knows it must shut down)
421 4.0.0 Tarpitting active for [xxx.xxx.xxx.xxx]. This indicates the connecting IP is blocked for reasons defined in Intrusion Prevention.
450 Requested mail action not taken: mailbox unavailable (E.g., mailbox busy)
451 Requested action aborted: local error in processing (the service can not access the assigned \temp\ folder)
451 4.7.1 This server is currently unavailable, please try later. (This is returned when Greylisting is enabled in AntiSpam)
452 Requested action not taken: insufficient system storage
500 Syntax error, command unrecognized (This may include errors such as command line too long)
501 Syntax error in parameters or arguments (no @ sign, or a missing bracket in the address)
502 Command not implemented (using HELO instead of EHLO)
503 Bad sequence of commands
504 Command parameter not implemented
550 Requested action not taken: mailbox unavailable (E.g., mailbox not found, no access)
551 User not local; please try
552 Requested mail action aborted: exceeded storage allocation
553 Requested action not taken: mailbox name not allowed (E.g., mailbox syntax incorrect)
554 Transaction failed