Enhanced Mail System Status Codes (RFC1893)
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2019-Feb-12
Internet Society Requests For Comment (RFCs)
There currently is not a standard mechanism for the reporting of mail system errors except for the limited set offered by SMTP and the system specific text descriptions sent in mail messages. There is a pressing need for a rich machine readable status code for use in delivery status notifications [DSN]. This document proposes a new set of status codes for this purpose. [STANDARDS-TRACK]
Network Working Group G. Vaudreuil Request for Comments: 1893 Octel Network Services Category: Standards Track January 1996
Enhanced Mail System Status Codes
Status of this Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
There currently is not a standard mechanism for the reporting of mail system errors except for the limited set offered by SMTP and the system specific text descriptions sent in mail messages. There is a pressing need for a rich machine readable status code for use in delivery status notifications [DSN]. This document proposes a new set of status codes for this purpose.
SMTP [SMTP] error codes have historically been used for reporting mail system errors. Because of limitations in the SMTP code design, these are not suitable for use in delivery status notifications. SMTP provides about 12 useful codes for delivery reports. The majority of the codes are protocol specific response codes such as the 354 response to the SMTP data command. Each of the 12 useful codes are each overloaded to indicate several error conditions each. SMTP suffers some scars from history, most notably the unfortunate damage to the reply code extension mechanism by uncontrolled use. This proposal facilitates future extensibility by requiring the client to interpret unknown error codes according to the theory of codes while requiring servers to register new response codes.
The SMTP theory of reply codes partitioned in the number space such a manner that the remaining available codes will not provide the space needed. The most critical example is the existence of only 5 remaining codes for mail system errors. The mail system classification includes both host and mailbox error conditions. The remaining third digit space would be completely consumed as needed to indicate MIME and media conversion errors and security system errors.
A revision to the SMTP theory of reply codes to better distribute the error conditions in the number space will necessarily be incompatible with SMTP. Further, consumption of the remaining reply-code number
Vaudreuil Standards Track [Page 1]
RFC 1893 Mail System Status Codes January 1996
space for delivery notification reporting will reduce the available codes for new ESMTP extensions.
The following proposal is based on the SMTP theory of reply codes. It adopts the success, permanent error, and transient error semantics of the first value, with a further description and classification in the second. This proposal re-distributes the classifications to better distribute the error conditions, such as separating mailbox from host errors.
2. Status Codes
This document defines a new set of status codes to report mail system conditions. Thes...