SMTP Reply Codes

 Code  Description
211   System status, or system help reply.
214   Help message.
220   Domain service ready.Ready to start TLS.
221   Domain service closing transmission channel.
250   OK, queuing for node node started.Requested mail action okay, completed.
251   OK, no messages waiting for node node.User not local, will forward to forwardpath.
252   OK, pending messages for node node started.
    Cannot VRFY user (e.g., info is not local), but will take message for this user and attempt delivery.
253   OK, messages pending messages for node node started.
354   Start mail input; end with <CRLF>.<CRLF>.
355   Octet-offset is the transaction offset.
421   Domain service not available, closing transmission channel.
432   A password transition is needed.
450   Requested mail action not taken: mailbox unavailable.ATRN request refused.
451   Requested action aborted: local error in processing.Unable to process ATRN request now
452   Requested action not taken: insufficient system storage.
453   You have no mail.
454   TLS not available due to temporary reason.Encryption required for requested authentication mechanism.
458   Unable to queue messages for node node.
459   Node node not allowed: reason.
500   Command not recognized: command.Syntax error.
501   Syntax error, no parameters allowed.
502   Command not implemented.
503   Bad sequence of commands.
504   Command parameter not implemented.
521   Machine does not accept mail.
530   Must issue a STARTTLS command first.Encryption required for requested authentication mechanism.
534   Authentication mechanism is too weak.
538   Encryption required for requested authentication mechanism.
550   Requested action not taken: mailbox unavailable.
551   User not local; please try forwardpath.
552   Requested mail action aborted: exceeded storage allocation.
553   Requested action not taken: mailbox name not allowed.
554   Transaction failed.