RFC 1893 (rfc1893) - Page 3 of 15

Enhanced Mail System Status Codes

RFC 1893                Mail System Status Codes            January 1996


   The class sub-code provides a broad classification of the status.
   The enumerated values the class are defined as:

    2.X.X   Success

       Success specifies that the DSN is reporting a positive delivery
       action.  Detail sub-codes may provide notification of
       transformations required for delivery.

    4.X.X   Persistent Transient Failure

       A persistent transient failure is one in which the message as
       sent is valid, but some temporary event prevents the successful
       sending of the message.  Sending in the future may be successful.

    5.X.X   Permanent Failure

       A permanent failure is one which is not likely to be resolved by
       resending the message in the current form.  Some change to the
       message or the destination must be made for successful delivery.

   A client must recognize and report class sub-code even where
   subsequent subject sub-codes are unrecognized.

   The subject sub-code classifies the status.  This value applies to
   each of the three classifications.  The subject sub-code, if
   recognized, must be reported even if the additional detail provided
   by the detail sub-code is not recognized.  The enumerated values for
   the subject sub-code are:

       X.0.X   Other or Undefined Status

          There is no additional subject information available.

       X.1.X   Addressing Status

          The address status reports on the originator or destination
          address.  It may include address syntax or validity.  These
          errors can generally be corrected by the sender and retried.

       X.2.X   Mailbox Status

          Mailbox status indicates that something having to do with the
          mailbox has cause this DSN.  Mailbox issues are assumed to be
          under the general control of the recipient.






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