rfc1893.txt

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       X.4.2   Bad connection

          The outbound connection was established, but was otherwise
          unable to complete the message transaction, either because
          of time-out, or inadequate connection quality. This is
          useful only as a persistent transient error.

       X.4.3   Directory server failure

          The network system was unable to forward the message,
          because a directory server was unavailable.  This is useful
          only as a persistent transient error.

          The inability to connect to an Internet DNS server is one
          example of the directory server failure error.

       X.4.4   Unable to route

          The mail system was unable to determine the next hop for the
          message because the necessary routing information was
          unavailable from the directory server. This is useful for
          both permanent and persistent transient errors.



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RFC 1893                Mail System Status Codes            January 1996


          A DNS lookup returning only an SOA (Start of Administration)
          record for a domain name is one example of the unable to
          route error.

       X.4.5   Mail system congestion

          The mail system was unable to deliver the message because
          the mail system was congested. This is useful only as a
          persistent transient error.

       X.4.6   Routing loop detected

          A routing loop caused the message to be forwarded too many
          times, either because of incorrect routing tables or a user
          forwarding loop. This is useful only as a persistent
          transient error.

       X.4.7   Delivery time expired

          The message was considered too old by the rejecting system,
          either because it remained on that host too long or because
          the time-to-live value specified by the sender of the
          message was exceeded. If possible, the code for the actual
          problem found when delivery was attempted should be returned
          rather than this code.  This is useful only as a persistent
          transient error.

   3.6 Mail Delivery Protocol Status

       X.5.0   Other or undefined protocol status

          Something was wrong with the protocol necessary to deliver
          the message to the next hop and the problem cannot be well
          expressed with any of the other provided detail codes.

       X.5.1   Invalid command

          A mail transaction protocol command was issued which was
          either out of sequence or unsupported.  This is useful only
          as a permanent error.

       X.5.2   Syntax error

          A mail transaction protocol command was issued which could
          not be interpreted, either because the syntax was wrong or
          the command is unrecognized. This is useful only as a
          permanent error.




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       X.5.3   Too many recipients

          More recipients were specified for the message than could
          have been delivered by the protocol.  This error should
          normally result in the segmentation of the message into two,
          the remainder of the recipients to be delivered on a
          subsequent delivery attempt.  It is included in this list in
          the event that such segmentation is not possible.

       X.5.4   Invalid command arguments

          A valid mail transaction protocol command was issued with
          invalid arguments, either because the arguments were out of
          range or represented unrecognized features. This is useful
          only as a permanent error.

       X.5.5   Wrong protocol version

          A protocol version mis-match existed which could not be
          automatically resolved by the communicating parties.

   3.7 Message Content or Message Media Status

       X.6.0   Other or undefined media error

          Something about the content of a message caused it to be
          considered undeliverable and the problem cannot be well
          expressed with any of the other provided detail codes.

       X.6.1   Media not supported

          The media of the message is not supported by either the
          delivery protocol or the next system in the forwarding path.
          This is useful only as a permanent error.

       X.6.2   Conversion required and prohibited

          The content of the message must be converted before it can
          be delivered and such conversion is not permitted.  Such
          prohibitions may be the expression of the sender in the
          message itself or the policy of the sending host.

       X.6.3   Conversion required but not supported

          The message content must be converted to be forwarded but
          such conversion is not possible or is not practical by a
          host in the forwarding path.  This condition may result when
          an ESMTP gateway supports 8bit transport but is not able to



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          downgrade the message to 7 bit as required for the next hop.

       X.6.4   Conversion with loss performed

          This is a warning sent to the sender when message delivery
          was successfully but when the delivery required a conversion
          in which some data was lost.  This may also be a permanant
          error if the sender has indicated that conversion with loss
          is prohibited for the message.

       X.6.5   Conversion Failed

          A conversion was required but was unsuccessful.  This may be
          useful as a permanent or persistent temporary notification.

   3.8 Security or Policy Status

       X.7.0   Other or undefined security status

          Something related to security caused the message to be
          returned, and the problem cannot be well expressed with any
          of the other provided detail codes.  This status code may
          also be used when the condition cannot be further described
          because of security policies in force.

       X.7.1   Delivery not authorized, message refused

          The sender is not authorized to send to the destination.
          This can be the result of per-host or per-recipient
          filtering.  This memo does not discuss the merits of any
          such filtering, but provides a mechanism to report such.
          This is useful only as a permanent error.

       X.7.2   Mailing list expansion prohibited

          The sender is not authorized to send a message to the
          intended mailing list. This is useful only as a permanent
          error.

       X.7.3   Security conversion required but not possible

          A conversion from one secure messaging protocol to another
          was required for delivery and such conversion was not
          possible. This is useful only as a permanent error.







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       X.7.4   Security features not supported

          A message contained security features such as secure
          authentication which could not be supported on the delivery
          protocol. This is useful only as a permanent error.

       X.7.5   Cryptographic failure

          A transport system otherwise authorized to validate or
          decrypt a message in transport was unable to do so because
          necessary information such as key was not available or such
          information was invalid.

       X.7.6   Cryptographic algorithm not supported

          A transport system otherwise authorized to validate or
          decrypt a message was unable to do so because the necessary
          algorithm was not supported.

       X.7.7   Message integrity failure

          A transport system otherwise authorized to validate a
          message was unable to do so because the message was
          corrupted or altered.  This may be useful as a permanent,
          transient persistent, or successful delivery code.

4.   References

   [SMTP] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
       USC/Information Sciences Institute, August 1982.

   [DSN] Moore, K., and G. Vaudreuil, "An Extensible Message Format for
       Delivery Status Notifications", RFC 1894, University of
       Tennessee, Octel Network Services, January 1996.

5.   Security Considerations

   This document describes a status code system with increased
   precision.  Use of these status codes may disclose additional
   information about how an internal mail system is implemented beyond
   that currently available.

6.   Acknowledgments

   The author wishes to offer special thanks to Harald Alvestrand, Marko
   Kaittola, and Keith Moore for their extensive review and constructive
   suggestions.




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7.   Author's Address

   Gregory M. Vaudreuil
   Octel Network Services
   17060 Dallas Parkway
   Suite 214
   Dallas, TX 75248-1905

   Voice/Fax: [phone]
   EMail: [e-mail]









































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RFC 1893                Mail System Status Codes            January 1996


8.   Appendix - Collected Status Codes

       X.1.0     Other address status
       X.1.1     Bad destination mailbox address
       X.1.2     Bad destination system address
       X.1.3     Bad destination mailbox address syntax
       X.1.4     Destination mailbox address ambiguous
       X.1.5     Destination mailbox address valid
       X.1.6     Mailbox has moved
       X.1.7     Bad sender's mailbox address syntax
       X.1.8     Bad sender's system address

       X.2.0     Other or undefined mailbox status
       X.2.1     Mailbox disabled, not accepting messages
       X.2.2     Mailbox full
       X.2.3     Message length exceeds administrative limit.
       X.2.4     Mailing list expansion problem

       X.3.0     Other or undefined mail system status
       X.3.1     Mail system full
       X.3.2     System not accepting network messages
       X.3.3     System not capable of selected features
       X.3.4     Message too big for system

       X.4.0     Other or undefined network or routing status
       X.4.1     No answer from host
       X.4.2     Bad connection
       X.4.3     Routing server failure
       X.4.4     Unable to route
       X.4.5     Network congestion
       X.4.6     Routing loop detected
       X.4.7     Delivery time expired

       X.5.0     Other or undefined protocol status
       X.5.1     Invalid command
       X.5.2     Syntax error
       X.5.3     Too many recipients
       X.5.4     Invalid command arguments
       X.5.5     Wrong protocol version

       X.6.0     Other or undefined media error
       X.6.1     Media not supported
       X.6.2     Conversion required and prohibited
       X.6.3     Conversion required but not supported
       X.6.4     Conversion with loss performed
       X.6.5     Conversion failed





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       X.7.0     Other or undefined security status
       X.7.1     Delivery not authorized, message refused
       X.7.2     Mailing list expansion prohibited
       X.7.3     Security conversion required but not possible
       X.7.4     Security features not supported
       X.7.5     Cryptographic failure
       X.7.6     Cryptographic algorithm not supported
       X.7.7     Message integrity failure











































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