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FTP error code usage for more reliable mail service (RFC0630) Disclosure Number: IPCOM000003703D
Original Publication Date: 1974-Apr-10
Included in the Prior Art Database: 2000-Sep-13
Document File: 2 page(s) / 4K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Sussmann: AUTHOR



This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 74% 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.


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


Examples: No such user; No mailbox for that user; Can't access file

(because net users can't write in that mailbox).

451 Permanent failures due to the message itself.

Example: Line sent over TELNET connection is too long (MAIL command


453 Temporary failures

Examples: TELNET connection unexpectedly closed; Mailbox busy;

Unexpected local errors (such as failure to create scratch file).