Survey of FTP mail and MLFL
A survey of how ARPANET FTP servers handled mail and an alternative mail command
Lebling, P.D., "Survey of FTP mail and MLFL", RFC 751, DOI 10.17487/RFC0751, December 1978, <https://www.rfc-editor.org/info/rfc751>.
@misc{rfc751,
series = {Request for Comments},
number = 751,
howpublished = {RFC 751},
publisher = {RFC Editor},
doi = {10.17487/RFC0751},
url = {https://www.rfc-editor.org/info/rfc751},
author = {P.D. Lebling},
title = {{Survey of FTP mail and MLFL}},
pagetotal = 5,
year = 1978,
month = dec,
} RFC text
NWG/RFC 751 PDL 10 Dec 78 nnnnn
Network Working Group P. David Lebling
Request for Comments: 751 (PDL@MIT-DMS)
NIC: nnnnn 10 December 1978
SURVEY OF FTP MAIL AND MLFL
Two surveys of Arpanet Server hosts were run between September 20, 1978
and December 11, 1978. The intent was to determine the response of the
host's Server FTP program to:
(a) An attempt to mail to an unknown recipient at that host. The
purpose of this survey was two-fold. First, to determine whether the
host accepts mail for unknown recipients at all, and second, what
response the host gives if it does not accept such mail.
(b) An attempt to mail to a known recipient using the MLFL command
rather than the usual MAIL command. This survey was undertaken to
determine the extent of support for the MLFL command among Server hosts,
and the sort of reply received if the Server does not support MLFL. MLFL
is potentially a 'better' form of communication than mail as the message
is sent over a data connection rather than the command connection.
Using the data connection eliminates the 'end-of-mail' marker and
'command reader' problems sometimes encountered over the command
connection.
The ground rules of the survey were that all sites listed as Servers in
the MIT/SAIL Host table were surveyed. In many cases, a host listed as
a Server would not respond to an ICP at any time during the period of
the survey. Once a host responded with what seemed to me to be a
'definitive' answer, I marked it as such and stopped surveying it.
MLFL Survey
The algorithm used was to ICP to socket 3 of the server (the standard
old-FTP socket). Once a 300 response was received, I sent the MLFL
command. Where I had the name of a real mailbox at a site (a
Header-person, for example) I used that, otherwise the name "**". If a
site asked for a password (response 504) after the MLFL command I gave
"USER NETML" "PASS NETML" and retried the MLFL. If the server replied
with a 255 SOCK command, I listened for the data-connection to be
established. When it was, I transferred the mail file. Interestingly
enough, most sites implement an RFC queueing algorithm that will allow
the user site to attempt to establish the data-connection from its end.
NWG/RFC 751 PDL 10 Dec 78 nnnnn
Survey of FTP MAIL and MLFL
Complete FTP scripts may be found, if you are interested, on MIT-DM,
file NETDOC;MLFL SURVEY.
Sites are grouped by the general result they gave.
-site- -last ftp reply if lost- -when-
1) Sites that lost for various reasons:
BNL 530 NOT LOGGED IN. after MLFL
HARV-10 431 INVALID ENTRY - Try again after USER
LLL-MFE 454 Login please after SOCK
LONDON 000 INDRA FTP Version 2.00 ... after ICP
NBS-10 454 Login please after SOCK
WHARTON 454 DATA Connection error ... after SOCK
WPAFB-AFAL 454 Login please after SOCK
Note: "when" describes the last action performed by the surveyer before
the indicated anomalous response.
after ICP -- surveyer had done ICP to socket 3
after MLFL -- surveyer had sent MLFL command
after USER -- surveyer had sent USER NETML in response to
"504 Login please"
after SOCK -- surveyer had attempted to connect to specified
data socket
2) Sites that don't support MLFL and say so:
AFWL 501 ML<?>FL **
CCA-SPEECH 501 ML<?>FL **
EGLIN 501 ML<?>FL **
LBL 506 Command not implemented.
LONDON-VDH 500 Command unrecognized
UCLA-CCN 500 COMMAND UNRECOGNIZED
WPAFB 501 ML<?>FL **
3) Sites that support MLFL (or at least go through all the right
motions):
AMES-67 MIT-AI SRI-KL
BBN-TENEX MIT-DMS SU-AI
BBN-TENEXA MIT-MC SUMEX-AIM
BBN-TENEXD MIT-ML UCLA-ATS
BBN-TENEXE MIT-XX UCLA-SECURITY
BBN-UNIX NBS-UNIX USC-ECL
CCA-TENEX OFFICE-1 USC-ISI
CMU-10A PARC-MAXC USC-ISIB
CMU-10B PARC-MAXC2 USC-ISIC
NWG/RFC 751 PDL 10 Dec 78 nnnnn
Survey of FTP MAIL and MLFL
DEC-MARLBORO RADC-TOPS20 USC-ISIE
I4-TENEX RAND-RCC UTEXAS
ILL-UNIX RAND-UNIX
LL RUTGERS
LL-ASG SRI-KA
4) Sites that support MLFL but require "USER NETML" "PASS NETML"
(Multics):
MIT-MULTICS
RADC-MULTICS
5) Others:
a) Sites that might support it if I could mail to a real user (some of
these run operating systems that are "known to work", e.g. TENEX):
BBN-TENEXB 450 No such mailbox at this site.
CCA-SDMS 450 User Unknown
CCTC 451 User Not Recognized
CMU-10D 507 USER NOT FOUND: **
DTI 451 User Not Recognized
LL-11 450 User Unknown
LL-XN 450 User Unknown
NCSC 451 User Not Recognized
NOSC-CC 451 User Not Recognized
NOSC-SDL 451 User Not Recognized
NTIA-ITS 451 User Not Recognized
OFFICE-2 450 No such mailbox at this site.
RADC-XPER 451 User Not Recognized
SDAC-44 431 User name invalid
SDAC-UNIX 451 User Not Recognized
SRI-UNIX 451 User Not Recognized
b) Sites that either never responded to an ICP to socket 3, or were not
accepting FTP users:
ANL I4B-TENEX NOSC-SECURE1
ARPA-DMS ISI-SPEECH11 NSWC-WO
CMU-CMMP LBL-UNIX NUSC
CTO-DDS LLL-COMP NUSC-NPT
DTNSRDC MOFFET-ARC NWC
FNWC NADC NYU
GUNTER-UNIX NDRE PENT-UNIX
NWG/RFC 751 PDL 10 Dec 78 nnnnn
Survey of FTP MAIL and MLFL
MAIL Survey
The mechanics of the MAIL survey were similar to those of the MLFL
survey. The command was "MAIL Fzorkness" (an account unlikely to exist
on any host). The responses are grouped into a few general categories.
Complete FTP results may be found on MIT-DM, file NETDOC;MAIL SURVEY.
-site- -last response-
1) Sites that lost completely.
LONDON 000 INDRA FTP Version <>.00 ...
2) Sites that accept mail to an unknown recipient.
BNL MIT-ML USC-ISI
MIT-AI RAND-RCC USC-ISIB
MIT-DMS UCLA-CCN USC-ISIC
MIT-MC USC-ECL USC-ISIE
3) Sites that refuse mail to an unknown recipient (grouped by response).
SDAC-44 431 User name invalid
BBN-TENEX 450 No such mailbox at this site.
BBN-TENEXA 450 No such mailbox at this site.
BBN-TENEXB 450 No such mailbox at this site.
BBN-TENEXD 450 No such mailbox at this site.
BBN-TENEXE 450 No such mailbox at this site.
BBN-UNIX 450 User Unknown
CCA-SDMS 450 User Unknown
CCTC 451 User Unknown
EDN-UNIX 450 User Unknown
I4-TENEX 450 No such mailbox at this site.
ILL-UNIX 450 User unknown
LL 450 No such mailbox at LL
LL-ASG 450 User unknown
LL-XN 450 User unknown
MIT-MULTICS 450 Cannot locate mailbox for \Fzorkness\
MIT-XX 450 No such mailbox at this site.
NBS-UNIX 450 User Unknown
NCSC 450 User Unknown
NOSC-CC 450 User Unknown
NOSC-SDL 450 User Unknown
NTIA-ITS 450 User Unknown
OFFICE-1 450 No such mailbox at this site.
OFFICE-2 450 No such mailbox at this site.
PARC-MAXC 450 No such mailbox at this site.
NWG/RFC 751 PDL 10 Dec 78 nnnnn
Survey of FTP MAIL and MLFL
PARC-MAXC2 450 No such mailbox at this site.
RADC-XPER 450 User Unknown
RADC-MULTICS 450 Cannot locate mailbox for \Fzorkness\
RADC-TOPS20 450 No such mailbox at this site.
RAND-UNIX 450 User Unknown
RUTGERS 450 No such mailbox at this site.
SDAC-UNIX 450 User Unknown
SRI-KA 450 No such mailbox at this site.
SRI-KL 450 No such mailbox at this site.
SU-AI 450 I don't know anybody named Fzorkness
SUMEX-AIM 450 No such mailbox at this site.
UCLA-ATS 450 User Unknown
UCLA-SECURITY 450 User Unknown
UTEXAS 450 User Unknown
CCA-TENEX 451 No such mailbox at this site.
AFWL 501 MA<?>IL Fzorkness
CCA-SPEECH 501 MA<?>IL Fzorkness
EGLIN 501 MA<?>IL Fzorkness
WPAFB 501 MA<?>IL Fzorkness
AMES-67 503 COMMAND \MAIL FZORKNESS\ IGNORED: UNKNOWN USER
LBL 506 Command not implemented.
CMU-10A 507 % USER NOT FOUND: FZORKNESS
CMU-10B 507 % USER NOT FOUND: FZORKNESS
CMU-10D 507 % USER NOT FOUND: FZORKNESS
HARV-10 507 No such user as FZORKNESS
LLL-MFE 507 No such user as FZORKNESS
NBS-10 507 No such user as FZORKNESS
WHARTON 507 No such user as FZORKN
WPAFB-AFAL 507 No such user as FZORKNESS
4) Sites to which I was never able to connect, or which were not
accepting users.
ANL I4B-TENEX NOSC-SECURE1
ARPA-DMS ISI-SPEECH11 NSWC-WO
CMU-CMMP LBL-UNIX NUSC
CTO-DDS LL-11 NUSC-NPT
DEC-MARLBORO LLL-COMP NWC
DTI LONDON-VDH NYU
DTNSRDC MOFFETT-ARC SRI-UNIX
FNWC NADC SU-ISL
GUNTER-UNIX NDRE
AI ELI5
On this page
§1Testing FTP Mail Servers
RFC 751 reports the results of two surveys of ARPANET server hosts conducted between September 20 and December 11, 1978. The surveys tested how FTP servers responded to (1) attempts to send mail to unknown recipients and (2) attempts to use the MLFL command instead of the standard MAIL command.
The goal was to determine which servers accepted mail for unknown users, what error they returned when they refused, and to what extent the MLFL command (which sends mail over a data connection rather than the command connection, avoiding certain end-of-mail and command-reader problems) was supported across the network.
The RFC is a report card: the author tried mailing to made-up names at many computers, and separately tried a different kind of mail command, and wrote down what each computer said.
§2MLFL Command Results
The MLFL survey tested 56 server sites by connecting to socket 3 and sending the MLFL command. Seven sites failed to connect or gave anomalous responses (e.g., "INDRA FTP Version 2.00" crashes). Seven sites returned an unrecognized command error (501 or 500 response). Thirty-one sites appeared to support MLFL or proceed through all the right motions, though a few required authentication (USER/PASS) first.
The survey exposed wide variation: most sites that supported MLFL allowed the user to attempt the data connection from their own end, using an RFC queueing algorithm, rather than just listening. Some sites like MIT-MULTICS and RADC-MULTICS required specific credentials before accepting MLFL.
Of the computers tested, some understood the MLFL command and sent data, some said they did not understand it, and a few just crashed or refused to talk.
§3Mail to Unknown Recipients
The MAIL survey tested how servers responded to sending mail to a fake recipient ("Fzorkness"). Nine sites accepted mail for unknown recipients. Thirty-one sites refused with a 450 error ("No such mailbox") or similar. Seventeen sites returned other errors (user unknown, login required, etc.).
The results show that most servers were protective of their mail systems, refusing to accept messages for nonexistent users. However, a few sites (MIT-AI, MIT-DMS, MIT-MC, BNL, UCLA-CCN, RAND-RCC, and the USC-ISI group) did accept such mail, suggesting different philosophies about forward mail delivery and alias handling.
Most computers refused to accept mail for people they didn't know. A few accepted it anyway, maybe assuming the mail should be forwarded or queued.