Network Working Group C. Malamud
Internet-Draft Memory Palace Press
Expires: July 30, 2004 January 30, 2004
A No Soliciting SMTP Service Extension
draft-malamud-no-soliciting-05
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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This Internet-Draft will expire on July 30, 2004.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This Internet-Draft proposes an extension to SMTP for an electronic
mail equivalent to the real-world "No Soliciting" sign. In addition
to the service extension, a new message header and extensions to the
existing "received" message header are described.
Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, [RFC2119].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 The Spam Pandemic . . . . . . . . . . . . . . . . . . . . . 3
1.2 No Soliciting in the Real World . . . . . . . . . . . . . . 3
1.3 No Soliciting and Electronic Mail . . . . . . . . . . . . . 5
2. The No-Soliciting SMTP Service Extension . . . . . . . . . . 6
2.1 The EHLO Exchange . . . . . . . . . . . . . . . . . . . . . 7
2.2 Solicitation Class Keywords . . . . . . . . . . . . . . . . 7
2.2.1 Note on Choice of Solicitation Class Keywords . . . . . . . 8
2.3 The MAIL FROM Command . . . . . . . . . . . . . . . . . . . 8
2.4 Error Reporting and Enhanced Mail Status Codes . . . . . . . 9
2.5 Solicitation Mail Header . . . . . . . . . . . . . . . . . . 10
2.6 Insertion of Solicitation Keywords in Trace Fields . . . . . 10
2.7 Relay of Messages . . . . . . . . . . . . . . . . . . . . . 11
2.8 No Default Solicitation Class . . . . . . . . . . . . . . . 12
3. Security Considerations . . . . . . . . . . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . 13
4.1 The Mail Parameters Registry . . . . . . . . . . . . . . . . 13
4.2 Trace Fields . . . . . . . . . . . . . . . . . . . . . . . . 13
4.3 The Solicitation Class Keywords Registry . . . . . . . . . . 13
4.3.1 Guidance on Keyword Specification . . . . . . . . . . . . . 14
4.4 The Solicitation Mail Header . . . . . . . . . . . . . . . . 15
5. Author's Acknowledgements . . . . . . . . . . . . . . . . . 15
Informative References . . . . . . . . . . . . . . . . . . . 15
Normative References . . . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . 18
A. Collected ABNF Descriptions (Normative) . . . . . . . . . . 18
B. Example Solicitation Class Keywords (Non-Normative) . . . . 19
C. Status of This Document [To Be Removed Upon Publication] . . 19
C.1 RFC Category . . . . . . . . . . . . . . . . . . . . . . . . 19
C.2 Document Repository . . . . . . . . . . . . . . . . . . . . 19
C.3 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 19
C.4 Changes From Previous Drafts . . . . . . . . . . . . . . . . 20
Intellectual Property and Copyright Statements . . . . . . . 23
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1. Introduction
1.1 The Spam Pandemic
Unsolicited Bulk Email (UBE), otherwise known as spam, has become as
one of the most pressing issues on the Internet. One oft-quoted
study estimated that spam would cost businesses $13 billion in
2003.[Ferris] In April 2003, AOL reported that it had blocked 2.37
billion pieces of UBE in a single day.[CNET] And, in a sure sign that
UBE has become of pressing concern, numerous politicians have begun
to issue pronouncements and prescriptions for fighting this
epidemic.[Schumer][FTC]
A variety of mechanisms from the technical community have been
proposed and/or implemented to fight UBE:
o Whitelists are lists of known non-spammers. For example, Habeas,
Inc. maintains a Habeas User List (HUL) of people who have agreed
to not spam. By including a haiku in email headers and enforcing
copyright on that ditty, they enforce their anti-spamming terms of
service.[Habeas]
o Blacklists are lists of known spammers or ISPs that allow
spam.[ROKSO]
o Spam filters run client-side or server-side to filter out spam
based on whitelists, blacklists, and textual and header
analysis.[Assassin]
o A large number of documents address the overall technical
considerations for the control of
UBE[I-D.crocker-spam-techconsider], operational considerations for
SMTP agents[RFC2505], and various extensions to the protocols to
support UBE identification and filtering.
[I-D.danisch-dns-rr-smtp][I-D.daboo-sieve-spamtest][I-D.crouzet-amtp]
o Various proposals have been advanced for "do not spam" lists, akin
to the Federal Trade Commission's "Do Not Call" list for
telemarketers.[FTC.TSR]
1.2 No Soliciting in the Real World
Municipalities frequently require solicitors to register with the
town government. And, in many cases, the municipalities prohibit
soliciting in residences where the occupant has posted a sign. The
town of West Newbury, Massachusetts, for example, requires:
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"It shall be unlawful for any canvasser or solicitor to enter the
premises of a resident or business who has displayed a 'No
Trespassing' or 'No Soliciting' sign or poster. Further, it shall
be unlawful for canvassers or solicitors to ignore a resident or
business person's no solicitation directive or remain on private
property after its owner has indicated that the canvasser or
solicitor is not welcome."[Newbury]
Registration requirements for solicitors, particularly those
soliciting for political or religious reasons, have been the subject
of a long string of court cases. However, the courts have generally
recognized that individuals may post "No Soliciting" signs and the
government may enforce the citizen's desire. In a recent case where
Jehovah's Witnesses challenged a registration requirement in the city
of Stratton, Connecticut, saying they derived their authority from
the Scriptures, not the city. However, the court noted:
"A section of the ordinance that petitioners do not challenge
establishes a procedure by which a resident may prohibit
solicitation even by holders of permits. If the resident files a
'No Solicitation Registration Form' with the mayor, and also posts
a 'No Solicitation' sign on his property, no uninvited canvassers
may enter his property ..."[Watchtower]
Even government, which has a duty to promote free expression, may
restrict the use of soliciting on government property. In one case,
for example, a school district was allowed to give access to its
internal electronic mail system to the union that was representing
teachers, but was not required to do so to a rival union that was
attempting to gain the right to represent the teachers. The court
held that where property is not a traditional public forum "and the
Government has not dedicated its property to First Amendment
activity, such regulation is examined only for
reasonableness."[Perry]
The courts have consistently held that the state has a compelling
public safety reason for regulating solicitation. In Cantwell v.
Connecticut, the Supreme Court held that "a State may protect its
citizens from fraudulent solicitation by requiring a stranger in the
community, before permitting him publicly to solicit funds for any
purpose, to establish his identity and his authority to act for the
cause which he purports to represent."[Cantwell] And, in Martin v.
City of Struthers, the court noted that "burglars frequently pose as
canvassers, either in order that they may have a pretense to discover
whether a house is empty and hence ripe for burglary, or for the
purpose of spying out the premises in order that they may return
later."[Martin] The public safety issue applies very much to email,
where viruses can easily be delivered, in contrast to telephone
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solicitations where public safety is not nearly as much an issue.
This analysis is U.S.-centric, which is partly due to the background
of the author. However, the concept of prohibiting unwanted
solicitation does carry over to other countries:
o In Hong Kong, offices frequently post "no soliciting" signs.
o In the United Kingdom, where door-to-door peddlers are fairly
common, "no soliciting" signs are also common.
o In Australia, where door-to-door does not appear to be a pressing
social problem, there was legislation passed which outlawed the
practice of placing ads under wipers of parked cars.
o In France, which has a long tradition of door-to-door
solicitation, apartment buildings often use trespass laws to
enforce "no solicitation" policies.
o In the Netherlands, where door-to-door solicitation is not a
pressing issue, there is a practice of depositing free
publications in mailboxes. The postal equivalent of "no spam"
signs are quite prevalent and serve notice that the publications
are not desired.
1.3 No Soliciting and Electronic Mail
Many of the anti-spam proposals that have been advanced have great
merit, however none of them give notice to an SMTP agent in the
process of delivering mail that the receiver does not wish to receive
solicitations. Such a virtual sign would serve two purposes:
o It would allow the receiving system to "serve notice" that a
certain class of electronic mail is not desired.
o If a message is properly identified as belonging to a certain
class and that class of messages is not desired, transfer of the
message can be eliminated. Rather than filtering after delivery,
elimination of the message transfer can save network bandwidth,
disk space, and processing power.
This memo details a series of extensions to SMTP that have the
following characteristics:
o A service extension is described that allows a receiving Mail
Transport Agent (MTA) to signal the sending MTA that no soliciting
is in effect.
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o A header field for the sender of the message is defined that
allows the sender to flag a message as conforming to a certain
class.
o Trace fields for intermediate MTAs are extended to allow the
intermediate MTA to signal that a message is in a certain class.
Allowing the sender of a message to tag a message as being, for
example, unsolicited commercial email with adult content, allows
"good" spammers to conform to legal content labelling requirements by
governmental authorities, license agreements with service providers,
or conventions imposed by "whitelist" services. For senders of mail
who choose not to abide by these conventions, the intermediate trace
fields defined here allow the destination MTA or a designated
intermediate MTA to perform appropriate dispositions on the received
message.
This distributed approach to controlling UBE is advanced as an
alternative to centralized "do-not-spam" lists. Several important
caveats should be kept in mind by developers as they examine this
extension:
o This extension only provides a simple mean for senders, MTAs, and
receivers to assert keywords drawn from a common registry. This
extension does not deal with any issues of authentication or
consent.
o This extension does not specify what actions should be taken by a
recipient. In particular it does not specify that a particular
message should be accepted or deleted. That decision is well
outside of the scope of this extension and rests with the
recipient of the message.
o This extension does not relieve an intermediate MTA of its
obligations to relay a message.
2. The No-Soliciting SMTP Service Extension
Per [RFC2821], a "NO-SOLICITING" SMTP service extension is defined.
The service extension is declared during the initial "EHLO" SMTP
exchange. The extension has one optional parameter, consisting of
zero or more solicitation class keywords. Using the notation as
described in the Augmented BNF[RFC2234], the syntax is:
No-Soliciting-Service = "NO-SOLICITING"
[ SP Solicitation-keywords ]
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As will be further described below, the "Solicitation-keywords"
construct is used to indicate which classes of messages are not
desired. A keyword that is presented during the initial "EHLO"
exchange applies to all messages exchanged in this session. As will
also be further described below, additional keywords may be specified
on a per-recipient basis as part of the "MAIL FROM" command.
2.1 The EHLO Exchange
Keywords presented during the initial exchange indicate that no
soliciting is in effect for all messages delivered to this system.
It is equivalent to the sign on the door of an office building
announcing a company-wide policy. For example:
R: <wait for connection on TCP port 25>
S: <open connection to server>
R: 220 trusted.example.com SMTP service ready
S: EHLO untrusted.example.com
R: 250-trusted.example.com says hello
R: 250-NO-SOLICITING ADV
(The "ADV" keyword is an example of a keyword, the syntax of which is
described in the following section. The example values are drawn from
the non-normative appendix in Appendix B.)
Historical Note:
A similar proposal was advanced in 1999 by John Levine and Paul
Hoffman. This proposal used the SMTP greeting banner to specify
that unsolicited bulk email is prohibited on a particular system
through the use of the "NO UCE" keyword.[Levine] As the authors
note, their proposal has the potential of overloading the
semantics of the greeting banner, which may also be used for other
purposes (see, e.g., [Malamud]).
2.2 Solicitation Class Keywords
The "NO-SOLICITING" service extension uses solicitation class
keywords to signify classes of solicitations that are not accepted.
Solicitation class keywords are separated by commas.
There is no default solicitation class keyword for the service. In
other words, the following example is a "no-op":
R: 250-NO-SOLICITING
While the above example is a "no-op" it is useful for an MTA that
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wishes to pass along all messages, but would also like to pass along
"SOLICIT=" parameters on a message-by-message basis. The above
example invokes the use of the extension but does not signal any
restrictions by class of message.
Solicitation class keywords may be defined and registered as
specified in Section 4.3. Multiple solicitation class keywords are
separated by a comma to form a list:
Solicitation-keywords = registered-word 0*("," registered-word)
registered-word = ALPHA 0*(wordchar)
; registered-word(s) are registered
; with the IANA
wordchar = ("-" / "_" / ":" / ALPHA / DIGIT)
Developers should note that a "registered-word" MAY contain a
trailing wild card as part of the specification. See Section 4.3.1
for more details.
Several example solicitation class keywords are used throughout this
document and are further described in the non-normative Appendix B.
2.2.1 Note on Choice of Solicitation Class Keywords
This document does not specify which solicitation class keywords
shall or shall not be used on a particular message. The requirement
to use a particular keyword is a policy decision well outside the
scope of this document. In particular, the three keywords described
in this document are for illustrative purposes only and it is
expected that relevant policy bodies (e.g., governments, ISPs,
developers, or others) will specify appropriate keywords, the
definition of the meaning of those keywords, and any other policy
requirements, such as a requirement to use or not use this extension
in particular circumstances.
2.3 The MAIL FROM Command
"SOLICIT" is defined as a parameter for the "MAIL FROM" command. The
"SOLICIT" parameter is followed by an equal sign and a comma
separated list of solicitation class keywords. The syntax for this
parameter is:
Mail-From-Solicit-Parameter = "SOLICIT"
"=" Solicitation-keywords
; Solicitation-keywords, when used in MAIL FROM command
; MUST be identical to those in the Solicitation: header.
Note that white space is not permitted in this production.
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As an informational message, the "550" or "250" replies to the "RCPT
TO" command may also contain the "SOLICIT" parameter. If a message is
being rejected due to a solicitation class keyword match,
implementations SHOULD echo which solicitation classes are in effect.
See Section 2.4 for more on error reporting.
The receiving system may decide on a per-message basis the
appropriate disposition of messages:
R: <wait for connection on TCP port 25>
S: <open connection to server>
R: 220 trusted.example.com SMTP service ready
S: EHLO untrusted.example.com
R: 250-trusted.example.com says hello
R: 250-NO-SOLICITING ADV
S: MAIL FROM:<save@burntmail.example.com> SOLICIT=ADV:ADLT
S: RCPT TO:<coupon_clipper@moonlink.example.com>
R: 250 <coupon_clipper@moonlink.example.com>... Recipient ok
S: RCPT TO:<grumpy_old_boy@moonlink.example.com>
R: 550 <grumpy_old_boy@moonlink.example.com> SOLICIT=ADV:ADLT
In the previous example, the receiving MTA returned a "550" status
code, indicating that one message was being rejected. The
implementation also echoes back the currently set keywords for that
user on the "550" status message. The solicitation class keyword
which is echoed back is "ADV:ADLT" which illustrates how this
per-recipient solicitation class keyword has supplemented the base
"ADV" class declared in the "EHLO" exchange.
It should be carefully noted that this document does not specify
which actions a recipient should take if a particular solicitation
class keyword is present in a "MAIL FROM" command. The decision to
accept or reject a message is outside of the scope of this document.
Developers should also note that the source of the solicitation class
keywords used in the "MAIL FROM" command MUST be the "Solicitation:"
header described in Section 2.5 and MUST NOT be supplemented by
additional solicitation class keywords derived from the "Received:"
header trace fields which are described in Section 2.6.
2.4 Error Reporting and Enhanced Mail Status Codes
If a session between two MTAs is using both the "NO-SOLICITING"
extension and the Enhanced Mail Status Codes as defined in [RFC3463]
and a message is rejected based on the presence of a "SOLICIT"
parameter, the correct error message to return will usually be
"5.7.1", defined as "the sender is not authorized to send to the
destination ... [because] of per-host or per-recipient filtering."
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Other codes, including temporary status codes, may be more
appropriate in some circumstances and developers should look to
[RFC3463] on this subject. An example of such a situation might be
the use of quotas or size restrictions on messages by class. An
implementation MAY impose limits such as message size restrictions
based on solicitation classes, and when such limits are exceed they
SHOULD be reported using whatever status code is appropriate for that
limit.
In all cases, an implementation SHOULD include a
"Mail-From-Solicit-Parameter" on a"250" reply to the "MAIL FROM"
command. The parameter SHOULD includes the solicitation class
keyword(s) that matched. In addition to the solicitation class
keyword(s) that matched, an implementation MAY include additional
solicitation class keywords that are in effect.
2.5 Solicitation Mail Header
Per [RFC2822], a new "Solicitation:" header field is defined which
contains one or more solicitation class keywords.
Solicitation-header = "Solicitation:" 1*SP Solicitation-keywords
An example of this header follows:
To: Coupon Clipper <coupon_clipper@moonlink.example.com>
From: Spam King <save@burntmail.example.com>
Solicitation: ADV,ADV:ADLT
Several proposals, particularly legal ones, have suggested requiring
the use of keywords in the "Subject:" header. While embedding
information in the "Subject:" header may provide visual cues to end
users, it does not provide a straightforward set of cues for computer
programs such as mail transfer agents. As with embedding a "no
solicitation" message in a greeting banner, this overloads the
semantics of the "Subject:" header. Of course, there is no reason
why both mechanisms can't be used, and in any case the
"Solicitation:" header could be automatically inserted by the
sender's Mail User Agent (MUA) based on the contents of the subject
line.
2.6 Insertion of Solicitation Keywords in Trace Fields
The "Solicitation:" mail header is only available to the sending
client. RFCs 2821 and 2822 are quite specific that intermediate MTAs
shall not change message headers, with the sole exception of the
"Received:" trace field. Since many current systems use an
intermediate relay to detect unsolicited mail, an addition to the
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"Received:" header is described.
[RFC2821] documents the following productions for the "Received:"
header in a mail message:
; From RFC 2821
With = "WITH" FWS Protocol CFWS
Protocol = "ESMTP" / "SMTP" / Attdl-Protocol
Additionally, [RFC2822] defines a comment field as follows:
; From RFC 2822
comment = "(" *([FWS] ccontent) [FWS] ")"
ccontent = ctext / quoted-pair / comment
The "Mail-From-Solicit-Parameter" defined in Section 2.3 above is a
restricted form of ctext, yielding the following production:
With-Solicit = "WITH" FWS Protocol
"(" [FWS] comment [FWS] ")"
comment = "(" *([FWS] ccontent) [FWS] ")"
ccontent = ctext / quoted-pair /
comment / Mail-From-Solicit-Parameter
; The Mail-From-Solicit-Parameter
; is a restricted form of ctext
An example of a Received: header from a conforming MTA is as follows:
Received: by foo-mta.example.com with
ESMTP (SOLICIT=ADV,ADV:ADLT) ; Sat, 9 Aug 2003
16:54:42 -0700 (PDT)
It should be noted that keywords presented in trace fields may not
agree with those found in the "Solicitation:" header and trace fields
may exist even if the header is not present. When determing which
keywords are applicable to a particular exchange of messages,
implementors SHOULD examine any keywords found in the "Solicitation:"
header. Implementors MAY examine other keywords found in the trace
fields.
2.7 Relay of Messages
The "NO-SOLICITING" service extension, if present, applies to all
messages handled by the receiving Message Transfer Agent (MTA),
including those messages intended to be relayed to another system.
When relaying a message which was received in which the "SOLICIT"
parameter was set on the "MAIL FROM" command, the MTA MUST faithfully
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relay the "SOLICIT" parameter when delivering the message to an SMTP
server that supports this extension.
The "SOLICIT" parameter on a "MAIL FROM" command can be derived from
a variety of sources, including receipt of a message from a
conforming SMTP server. An SMTP server MAY, for operational reasons
as defined in Section 7.7 of [RFC2821], set this parameter after
detecting the presence of the "Solicitation:" header field when
receiving a message from a non-conforming MTA.
2.8 No Default Solicitation Class
Implementations of "NO-SOLICITING" service extension SHOULD NOT
enable specific solicitation class keywords as a default in their
software. There are some indications that some policy makers may
view a default filtering in software as a prior restraint on
commercial speech. In other words, because the person installing and
using the software did not make an explicit choice to enable a
certain type of filtering, some might argue that such filtering was
not desired.
Likewise, it is recommended that a system administrator installing
software SHOULD NOT enable per-recipient filtering by default for a
user. Again, individual users should specifically request any
additional solicitation class keywords.
The mechanism for an individual user to communicate their desire to
enable certain types of filtering is outside the scope of this
document.
3. Security Considerations
This extension does not provide authentication of senders or other
measures intended to promote security measures during the message
exchange process.
In particular, this document does not address the circumstances under
which a sender of electronic mail should or should not use this
extension and does not address the issues of whether consent to send
mail has been granted.
This might lead to a scenario in which a sender of electronic mail
begins to use this extension well before the majority of end users
have begun to use it. In this scenario, the sender might wish to use
the absence of the extension on the receiving MTA as an implication
of consent to receive mail. Non-use of the "NO-SOLICITING" extension
by a receiving MTA SHALL NOT indicate consent.
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4. IANA Considerations
There are four IANA considerations presented in this draft:
1. Addition of the "NO-SOLICITING" service extension to the Mail
Parameters registry.
2. Documentation of the use of comments in trace fields.
3. Creation of a Solicitation Class Keywords registry.
4. Creation of a "Solicitation:" mail header, which does not
currently raise any IANA considerations.
4.1 The Mail Parameters Registry
The IANA Mail Parameters registry documents SMTP service extensions.
The "NO-SOLICITATION" service extension would need to be added to
this registry as follows.
Keywords Description Reference
------------ ------------------------------ ---------
NO-SOLICITING Notification of no soliciting. [XXXX]
The parameters subregistry would need to be modified as follows:
Service Ext EHLO Keyword Parameters Reference
----------- ------------ ----------- ---------
No Soliciting NO-SOLICITING Solicitation-keywords [XXXX]
4.2 Trace Fields
The Mail Parameters registry would need to be modified to note the
use of the comment facility in trace fields to indicate Solicitation
Class Keywords.
4.3 The Solicitation Class Keywords Registry
A new registry (or a subregistry of Mail Parameters) would need to be
established for Solicitation Class Keywords. The registry would
contain the following fields:
1. Solicitation Class Keyword Name
2. Solicitation Class Keyword Description
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3. Solicitation Class Keyword Reference
The Name field conforms to the syntax of the "Solicitation-keywords"
in Section 2.2 of this draft. The Description field consists of text.
The Reference field should include a URI with further information.
Per the policies outlined in [RFC2434], it is recommended that the
IESG request the IANA to appoint a Designated Expert to administer
this registry. Authority for solicitation class keywords in this
registry will come in some cases from published RFCs, but in other
cases will come from applicable laws or regulations. It is
recommended that any non-RFC derived solicitation class keywords be
documented in future informational RFCs to provide a consistent set
of references.
Policies for the administration of this registry shall be developed
by the IANA and may include the automated processing of registration
requests.
4.3.1 Guidance on Keyword Specification
A set of keywords beginning with a common prefix may be registered
with the IANA by specifying the prefix followed by wild card
specified as a single asterisk ("*") and shall be considered a single
registry entry. The "keyword reference" field of the registry SHOULD
contain a reference that documents the values this solicitation class
keyword may contain if the trailing wild card is specified in the
"keyword name" field of the registry.
Note to Developers: In designing client and server solutions based
on this extension, it is important to remember to design your code
to take into account the possible use of these trailing wildcards.
See the "Solicitation-keywords" production in Section 2.2 for
valid characters and delimiters.
This facility can be used to insert a "score" or category tag by an
intermediate MTA. For example, a solicitation class keyword "WMA:*"
might be used as follows:
Received: by foo-mta.example.com with
ESMTP (WMA:SBRule:Haven_Domain,WMA:SBScore:10) ; Sat, 9 Aug 2003
16:54:42 -0700 (PDT)
Because of the wildcard provision, the IANA MAY require that each
solicitation class keyword name have a unique beginning sequence. For
example, registering sequences such as "ADV" and "ADV:ADLT" as
different names might require implementations to differentiate
between classes that use a wildcard and those that do not.
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4.4 The Solicitation Mail Header
There is currently no registry defined for mail headers. If such a
registry were to exist, the "Solicitation:" header field would need
to be added to it.
5. Author's Acknowledgements
The author would like to thank Rebecca Malamud for many discussions
and ideas that led to this proposal and to John C. Klensin and
Marshall T. Rose for their extensive input on how it could be
properly implemented in SMTP. Eric Allman, Steven M. Bellovin, Kent
Crispin, Dave Crocker, Ned Freed, Curtis Generous, Arnt Gulbrandsen,
John Levine, Keith Moore, Hector Santos, Paul Vixie, and Pindar Wong
kindly provided reviews of the draft and/or suggestions for
improvement. Information about soliciting outside the U.S. was
received from Rob Blokzijl, Jon Crowcroft, Christian Huitema, Geoff
Huston, and Pindar Wong. John Levine pointed out the contrast
between this proposal and "do not spam" lists. As always, all errors
and omissions are the responsibility of the author.
Informative References
[Assassin]
Mason, J., "Spamassassin - Mail Filter to Identify Spam
Using Text Analysis", Version 2.55, May 2003, <http://
www.mirror.ac.uk/sites/spamassassin.taint.org/
spamassassin.org/doc/spamassassin.html>.
[CNET] CNET News.Com, "AOL touts spam-fighting prowess", April
2003, <http://news.com.com/2100-1025-998944.html>.
[Cantwell]
U.S. Supreme Court, "Cantwell v. State of Connecticut",
310 U.S. 296 (1940), May 1940, <http://
caselaw.lp.findlaw.com/scripts/
getcase.pl?court=US&vol=310&invol=296>.
[FTC] Federal Trade Commission, "Federal, State, Local Law
Enforcers Target Deceptive Spam and Internet Scams",
November 2002, <http://www.ftc.gov/opa/2002/11/
nenetforcema.htm>.
[FTC.TSR] Federal Trade Commission, "Telemarketing Sales Rule",
Federal Register Vol. 68, No. 19, January 2003, <http://
www.ftc.gov/os/2002/12/tsrfinalrule.pdf>.
[Ferris] Associated Press, "Study: Spam costs businesses $13
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billion", January 2003, <http://www.cnn.com/2003/TECH/
biztech/01/03/spam.costs.ap/index.html>.
[Habeas] Habeas, Inc., "Habeas Compliant Message", April 2003,
<http://www.habeas.com/services/hcm.htm>.
[I-D.crocker-spam-techconsider]
Crocker, D., "Technical Considerations for Spam Control
Mechanisms", draft-crocker-spam-techconsider-02 (work in
progress), May 2003.
[I-D.crouzet-amtp]
Crouzet, B., "Authenticated Mail Transfer Protocol",
draft-crouzet-amtp-01 (work in progress), October 2003.
[I-D.daboo-sieve-spamtest]
Daboo, C., "SIEVE Spamtest and Virustest Extensions",
draft-daboo-sieve-spamtest-04 (work in progress), October
2003.
[I-D.danisch-dns-rr-smtp]
Danisch, H., "A DNS RR for simple SMTP sender
authentication", draft-danisch-dns-rr-smtp-03 (work in
progress), October 2003.
[Levine] Levine, J. and P. Hoffman, "Anti-UBE and Anti-UCE Keywords
in SMTP Banners", Revision 1.1, March 1999, <http://
www.cauce.org/proposal/smtp-banner-rfc.shtml>.
[Malamud] Malamud, C., "An Internet Prayer Wheel", Mappa.Mundi
Magazine, August 1999, <http://mappa.mundi.net/
cartography/Wheel/>.
[Martin] U.S. Supreme Court, "Martin v. City of Struthers, Ohio",
319 U.S. 141 (1943), May 1943, <http://
caselaw.lp.findlaw.com/scripts/
getcase.pl?court=US&vol=319&invol=141>.
[Newbury] The Town of West Newbury, Massachusetts, "Soliciting/
Canvassing By-Law", Chapter 18 Section 10, March 2002,
<http://www.town.west-newbury.ma.us/Public_Documents/
WestNewburyMA_Bylaws/chapter18>.
[Perry] U.S. Supreme Court, "Perry Education Association v. Perry
Local Educators' Association", 460 U.S. 37 (1983),
February 1983, <http://caselaw.lp.findlaw.com/scripts/
getcase.pl?court=US&vol=460&invol=37>.
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draft-malamud-no-soliciting No-Solicit January 2004
[RFC2505] Lindberg, G., "Anti-Spam Recommendations for SMTP MTAs",
BCP 30, RFC 2505, February 1999.
[ROKSO] Spamhaus.Org, "Register of Known Spam Operations",
November 2003, <http://www.spamhaus.org/rokso/
index.lasso>.
[Schumer] Charles, C., "Schumer, Christian Coalition Team Up to
Crack Down on Email Spam Pornography", June 2003, <http://
www.senate.gov/~schumer/SchumerWebsite/pressroom/
press_releases/PR01782.html>.
[Watchtower]
U.S. Supreme Court, "Watchtower Bible & Tract Society of
New York, Inc., et al. v. Village of Stratton et al.", 122
S.Ct. 2080 (2002), June 2002, <http://
caselaw.lp.findlaw.com/scripts/
getcase.pl?court=US&vol=000&invol=00-1737>.
Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
2001.
[RFC3463] Vaudreuil, G., "Enhanced Mail System Status Codes", RFC
3463, January 2003.
URIs
[1] <mailto:carl@media.org>
[2] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-04.html>
[3] <http://trusted.resource.org/no-solicit/
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draft-malamud-no-soliciting-05.html>
[4] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-03.html>
[5] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-04.html>
[6] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-02.html>
[7] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-03.html>
[8] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-01.html>
[9] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-02.html>
[10] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-00.html>
[11] <http://trusted.resource.org/no-solicit/
draft-malamud-no-soliciting-01.html>
Author's Address
Carl Malamud
Memory Palace Press
PO Box 300
Sixes, OR 97476
US
EMail: carl@media.org
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Appendix A. Collected ABNF Descriptions (Normative)
Solicitation-keywords = registered-word 0*("," registered-word)
registered-word = ALPHA 0*(wordchar)
; registered-word(s) are registered
; with the IANA
wordchar = ("-" / "_" / ":" / ALPHA / DIGIT)
; used in the initial EHLO exchange
No-Soliciting-Service = "NO-SOLICITING"
[ SP Solicitation-keywords ]
; used on the Solicitation: message header
Solicitation-header = "Solicitation:" 1*SP Solicitation-keywords
; used on the MAIL FROM command and replies,
; and on Received: headers.
Mail-From-Solicit-Parameter =
"SOLICIT" "=" Solicitation-keywords
; Solicitation-keywords, when used in
; the MAIL FROM command MUST be identical
; to those in the Solicitation: header.
; Used on Received: headers
With-Solicit = "WITH" FWS Protocol
"(" [FWS] comment [FWS] ")"
; From RFC 2822
comment = "(" *([FWS] ccontent) [FWS] ")"
ccontent = ctext / quoted-pair /
comment / Mail-From-Solicit-Parameter
; The Mail-From-Solicit-Parameter
; is a restricted form of ctext
; From RFC 2821
With = "WITH" FWS Protocol CFWS
Protocol = "ESMTP" / "SMTP" / Attdl-Protocol
Attdl-Protocol = Atom
Appendix B. Example Solicitation Class Keywords (Non-Normative)
Three solicitation class keywords are defined for use as examples in
this draft:
Keywords Description Reference
--------- -------------------------------- ---------
MAPS-UBE Unsolicited Bulk Email http://mail-abuse.org/
ADV Unsolicited Commercial Email http://www.spamlaws.com/
ADV:ADLT Sexually Explicit Commercial Mail http://www.spamlaws.com/
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MAPS-UBE is the standard advanced by the Mail Abuse Prevention System
(MAPS), which states:
An electronic message is "spam" IF: (1) the recipient's personal
identity and context are irrelevant because the message is equally
applicable to many other potential recipients; AND (2) the
recipient has not verifiably granted deliberate, explicit, and
still-revocable permission for it to be sent; AND (3) the
transmission and reception of the message appears to the recipient
to give a disproportionate benefit to the sender.
Numerous states have adopted the "ADV" and "ADV:ADLT" conventions.
We cite the spamlaws.com site as a reference because it provides an
excellent summary of the definitions and pointers to the relevant
statutes.
These three examples should not form part of the initial registry.
This section is non-normative and is not part of the definition of
the extension.
Appendix C. Status of This Document [To Be Removed Upon Publication]
C.1 RFC Category
This document will be submitted for publication as a Proposed
Standard.
C.2 Document Repository
The source for this document can be found at http://
trusted.resource.org/no-solicit.
C.3 Discussion
Discussions of this draft may be directed towards the ietf-smtp
mailing list which can be found at http://www.imc.org/ietf-smtp/.
Comments may be sent directly to the author at carl@media.org [1].
C.4 Changes From Previous Drafts
Changes from draft-malamud-no-soliciting-04 [2] to
draft-malamud-no-soliciting-05 [3]:
o This draft incorporates comments received in response to the IESG
last call.
o A discussion of what this proposal is not trying to accomplish was
added the end of Section 1.3.
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o The definition of solicitation class keywords has been changed.
"X-" words are no longer permitted. See Section 2.2.
o The solicitation class keywords previously defined in Section 2.2
have been moved to a non-normative appendix in Appendix B.
o The SYSTEM-WIDE and PER-RECIPIENT options have been eliminated.
Solicitation class keywords presented in the initial EHLO exchange
are in effect system-wide and additional keywords may be presented
on a per-recipient basis. See Section 2.
o Text has been added throughout the document to make clear that the
decision to reject a message is only taken by a recipient and that
the particular decision to take is outside the scope of this
draft.
o Section 3 ("Use of the Extension") of the previous draft has been
deleted. The material was non-normative.
Changes from draft-malamud-no-soliciting-03 [4] to
draft-malamud-no-soliciting-04 [5]:
o The Note on Open Issues has been removed and the abstract has been
made more precise.
o All examples now use subdomains of example.com.
o The "No-Soliciting-Service" production has been changed to make
clear that a set of keywords is not presented when the
"PER-RECIPIENT" option is used. See Section 2.
o A Note on Keywords has been added to make clear that the initial
three keywords choosen were simply to bootstrap the registry and
that the matter of which keywords to use and the definition of
those words is a policy decision well outside the scope of this
document. See Section 2.2.1.
o Solicitation Class Keywords are now carried as a comment to the
"ESMTP" protocol and additional language has been added clarifying
the relationship of keywords in "received:" headers to those in
the "Solicitation:" header. See Section 2.6.
o Some language has been added to further clarify what should happen
when dealing with a server that doesn't support the extension. See
Section 2.7.
o The Security Considerations section has been made more explicit.
See Section 3.
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o The Solicitation Class Keywords Registry has been clarified to
permit the use of a trailing wildcard in the "keyword name" field.
See Section 4.3.
Changes from draft-malamud-no-soliciting-02 [6] to
draft-malamud-no-soliciting-03 [7]:
o A discussion of Open Issues has been preprended to the document
and comments are requested.
Changes from draft-malamud-no-soliciting-01 [8] to
draft-malamud-no-soliciting-02 [9]:
o A real-world example of how the proposed service extension could
be used has been added (see Section 3.
o A discussion of the relative implementation difficulty of
"SYSTEM-WIDE" versus "PER-RECIPIENT" has been added (see Section
2.8).
o A discussion of the relationship of this proposal to centralized
"do not spam" lists has been added.
Changes from draft-malamud-no-soliciting-00 [10] to
draft-malamud-no-soliciting-01 [11]:
o The two service extensions previously proposed (
"SYSTEM-WIDE-NO-SOLICITING" and "PER-MESSAGE-NO-SOLICITING") have
been collapsed into a single "NO-SOLICITING" service extension (
See Section 2).
o "PER-MESSAGE" has been changed to "PER-RECIPIENT" to more properly
express the operation of the extension (see Section 3.3.
o A solicitation class keyword syntax is introduced to allow
different kinds of unsolicited mail to be considered (see Section
2.2).
o The "Solicitation:" header has been supplemented with an extended
"Received:" header syntax (see Section 2.6).
o A discussion of the use of Enhanced Mail Status Codes has been
included (see Section 2.4).
o A more extensive IANA Considerations section has been added,
including creation of a Solicitation Keywords registry (see
Section 4).
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Malamud Expires July 30, 2004 [Page 24]
