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FTP error code usage for more reliable mail service (RFC0630) Disclosure Number: IPCOM000003703D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2019-Feb-12
Document File: 3 page(s) / 4K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Sussman: AUTHOR

Related Documents

10.17487/RFC0630: DOI


Describes FTP reply-code usage in TENEX mail processing.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 61% of the total text.

Network Working Group Julie Sussman RFC # 630 BBN NIC # 30237 April 10, 1974

FTP Error Code Usage for More Reliable Mail Service


A major hindrance to providing reliable mail service is the lack of well-defined FTP error replies that would enable a mailing process to decide how to handle a failure. New FTP error codes are currently in the design stage, and a proposal will be announced soon. In the interim, we can get some improvement by simply defining how we intend to use the current FTP codes. The purpose of this RFC is to inform all sites of how TENEX sites will use and interpret the codes starting in the near future.


The FTP error codes defined for failure to perform a file action (including mail) are:

450 File not found 451 File access denied to you 452 Data connection closed 453 Insufficient storage 454 Cannot connect to your data socket

450, 451, and 453 are applicable to both the MAIL and MLFL commands, while 452 and 454 are only meaningful for MLFL.


There are more possible causes of failure to deliver mail than the ones defined above. Implementors of FTP servers thus had to make arbitrary assignments of error conditions to defined codes. As a result, although the text of the reply might distinguish these conditions for the benefit of human users, the code doesn’t distinguish them for the benefit of processes.

The minimum distinction needed by the TENEX mail-sending processes is between permanent and non-permanent failures. In the latter case, the process will repeatedly try to deliver the mail for several days.

Sussman [Page 1]

RFC 630 FTP Error Code Usage for Mail Service April 1974


The following changes will be installed at TENEX sites over the next couple of months.


The TENEX FTP server will continue to use 452 and 454 as specified for the MLFL command.

For MAIL and MLFL, it will send the other codes as follows:

450 Permanent failures due to the user addressed in the Mail or MLFL command.

Examples: No such...