Individual Submission S. Moonesamy, Ed. Internet-Draft December 11, 2011 Obsoletes: 2369 (if approved) Intended status: Standards Track Expires: June 13, 2012 The Use of URIs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields draft-moonesamy-rfc2369bis-00 Abstract The mailing list command specification header fields are a set of structured fields to be added to email messages sent by email distribution lists. Each header field typically contains a URI (usually mailto) locating the relevant information or performing the command directly. The three core header fields described in this document are List-Help, List-Subscribe, and List-Unsubscribe. There are three other header fields described here which, although not as widely applicable, will have utility for a sufficient number of mailing lists to justify their formalization here. These are List-Post, List-Owner and List-Archive. By including these header fields, mailing list managers can make it possible for mail user agents to provide automated tools for users to perform list functions. This could take the form of a menu item, push button, or other user interface element. The intent is to simplify the user experience, providing a common interface to the often cryptic and varied mailing list manager commands. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on June 13, 2012. Moonesamy Expires June 13, 2012 [Page 1]
Internet-Draft URIs for Core Mailing List Commands December 2011 Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Moonesamy Expires June 13, 2012 [Page 2]
Internet-Draft URIs for Core Mailing List Commands December 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Note . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. The Command Syntax . . . . . . . . . . . . . . . . . . . . . . 4 3. The List Header Fields . . . . . . . . . . . . . . . . . . . . 6 3.1. List-Help . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. List-Unsubscribe . . . . . . . . . . . . . . . . . . . . . 7 3.3. List-Subscribe . . . . . . . . . . . . . . . . . . . . . . 8 3.4. List-Post . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5. List-Owner . . . . . . . . . . . . . . . . . . . . . . . . 9 3.6. List-Archive . . . . . . . . . . . . . . . . . . . . . . . 9 3.7. List-Id . . . . . . . . . . . . . . . . . . . . . . . . . 10 4. Supporting Nested Lists . . . . . . . . . . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . . 12 Appendix A. Appendix . . . . . . . . . . . . . . . . . . . . . . 12 A.1. Client Implementation . . . . . . . . . . . . . . . . . . 12 A.1.1. Guidelines . . . . . . . . . . . . . . . . . . . . . . 12 A.1.2. Implementation Options . . . . . . . . . . . . . . . . 13 A.1.2.1. Key combinations and command lines . . . . . . . . 13 A.1.2.2. Menu items . . . . . . . . . . . . . . . . . . . . 13 A.1.2.3. Push Buttons and Pallettes . . . . . . . . . . . . 13 A.1.2.4. Feedback to the User . . . . . . . . . . . . . . . 14 A.2. Changes from RFC 2369 . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14 Moonesamy Expires June 13, 2012 [Page 3]
Internet-Draft URIs for Core Mailing List Commands December 2011 1. Introduction RFC 2369 [RFC2369] defined additional header fields to be added to email messages sent by mailing list managers (MLMs). The content of each new header field is typically a URI [RFC3986] - usually mailto [RFC6068] - which identifies the relevant information or performs the command directly. These headers fields are optional. Significant functionality and convenience can be gained by including them. The List-Help header field provides an access point to detailed user support information, and accommodates almost all existing mailing list managers command sets. The List-Subscribe and List-Unsubscribe header fields provide access to two functions commonly requested by mailing list subscribers. The description of command syntax provided by the header fields can be used by mail user agents (MUAs) to provide simplified and consistent user access to mailing list functions. This could take the form of menu items, push buttons, or other user interface elements. The intent is to simplify the user experience, providing a common interface to the often cryptic and varied mailing list manager commands. Consideration has been given to avoiding the creation of too many header fields, while at the same time avoiding the overloading of individual header fields and keeping the syntax clear and simple. The use of these header fields does not remove the requirement to support the -Request command address for mailing lists [RFC2142]. This document obsoletes RFC 2369 [RFC2369]. 1.1. 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 [RFC2119]. 1.2. Note This Internet-Draft can be discussed on the apps-discuss@ietf.org mailing list. [RFC-Editor: please remove this paragraph] 2. The Command Syntax The list header fields are subject to the encoding and character Moonesamy Expires June 13, 2012 [Page 4]
Internet-Draft URIs for Core Mailing List Commands December 2011 restrictions for mail headers fields as described in [RFC5322]. The contents of the list header fields mostly consist of angle- bracket ('<', '>') enclosed URIs [RFC3986], with internal whitespace being ignored. mailing list managers MUST NOT insert whitespace within the brackets. Client applications SHOULD treat any whitespace, that might be inserted by poorly behaved mailing list managers, as characters to ignore. A list of multiple, alternate, URIs MAY be specified by a comma- separated list of angle-bracket enclosed URIs. The URIs have order of preference from left to right. The client application should use the left most protocol that it supports, or knows how to access by a separate application. By this mechanism, protocols like http may be specified while still providing the basic mailto support for those clients who do not have access to non-mail protocols. The client should only use one of the available URIs for a command, using another only if the first one used failed. The use of URIs allows for the use of the syntax with existing URI supporting applications. As the standard for URIs is extended, the list header fields will gain the benefit of those extensions. Additionally, the use of URIs provides access to multiple transport protocols (such as ftp and http) although it is expected that the "mailto" protocol [RFC6068] will be the focus of most use of the list header fields. Use of non-mailto protocols should be considered in light of those users who do not have access to the specified mechanism (those who only have email - with no web access). Command syntaxes requiring variable fields to be set by the client (such as including the user's email address within a command) are not supported by this implementation. However, mailing list managers using such syntaxes should still take advantage of the List-Help field to provide the user with detailed instructions as needed or - perhaps more usefully - provide access to some form of structured command interface such as an HTML-based form. The additional complications of supporting variable fields within the command syntax was determined to be too difficult to support by this protocol and would compromise the likelihood of implementation by software authors. To allow for future extension, it is recommended that client applications follow the guidelines below for handling the contents of the header fields described in this document: Moonesamy Expires June 13, 2012 [Page 5]
Internet-Draft URIs for Core Mailing List Commands December 2011 1. Except where noted for specific header fields, if the content of the header field (following any leading whitespace, including comments) begins with any character other than the opening angle bracket '<', the header field SHOULD be ignored. 2. Any characters following an angle bracket enclosed URI SHOULD be ignored, unless a comma is the first non-whitespace/comment character after the closing angle bracket. 3. If a sub-item (comma-separated item) within the field is not an angle-bracket enclosed URI, the remainder of the field (the current, and all subsequent, sub-items) SHOULD be ignored. 3. The List Header Fields This document presents header fields which will provide the command syntax description for the 'core' and key secondary functions of most mailing list managers. The header fields implemented on a given mailing list SHOULD be included on all messages distributed by the list (including command responses to individual users), and on other messages where the message clearly applies to one distinct mailing list. There MUST be no more than one of each header field present in any given message. These header fields MUST only be generated by mailing list managers, not by MUAs. Mailing list managers generating the list header fields SHOULD include a mailto based command, in addition to any other protocols used, in order to support users who do not have access to non-mail-based protocols. 3.1. List-Help The List-Help header field is the most important of the header fields described in this document. It is acceptable for a mailing list manager to include only this header field, since by definition it can direct the user to complete instructions for all other commands. Typically, the URI specified would request the help file, perhaps incorporating an HTML form for list commands, for the list, and alternatively provide access to an instructive website. Examples: Moonesamy Expires June 13, 2012 [Page 6]
Internet-Draft URIs for Core Mailing List Commands December 2011 List-Help: <mailto:list-request@example.com?subject=help> (List Instructions) List-Help: <mailto:list-request@example.com?body=info> List-Help: <mailto:list-info@example.com> (Info about the list) List-Help: <http://www.example.com/list/>, <mailto:list-info@example.com> List-Help: <ftp://ftp.example.com/list.txt> (FTP), <mailto:list-request@example.com?subject=help> 3.2. List-Unsubscribe The List-Unsubscribe header field describes the command (preferably using mail) to directly unsubscribe the user (removing them from the list). Examples: List-Unsubscribe: <mailto:list-request@example.com?subject=unsubscribe> List-Unsubscribe: (Use this command to get off the list) <mailto:list-request@example.com?body=unsubscribe%20list> List-Unsubscribe: <mailto:list-remove@example.com> Moonesamy Expires June 13, 2012 [Page 7]
Internet-Draft URIs for Core Mailing List Commands December 2011 List-Unsubscribe: <http://www.example.com/list.cgi?cmd=unsub&lst=list>, <mailto:list-request@example.com?subject=unsubscribe> 3.3. List-Subscribe The List-Subscribe header field describes the command (preferably using mail) to directly subscribe the user (request addition to the list). Examples: List-Subscribe: <mailto:list-request@example.com?subject=subscribe> List-Subscribe: (Use this command to join the list) <mailto:list-request@example.com?body=subscribe%20list> List-Subscribe: <mailto:list-add@example.com> List-Subscribe: <http://www.example.com/list.cgi?cmd=sub&lst=list>, <mailto:list-request@example.com?body=subscribe%20list> 3.4. List-Post The List-Post header field describes the method for posting to the mailing list. This is typically the email address of the mailing list. It can also be the email address of a moderator, or potentially some other form of submission. For the special case of a mailing list that does not allow posting (e.g., an announcements list), the List-Post field may contain the special value "NO". Examples: Moonesamy Expires June 13, 2012 [Page 8]
Internet-Draft URIs for Core Mailing List Commands December 2011 List-Post: <mailto:list@example.com> List-Post: <mailto:list-moderator@example.com> (Postings are Moderated) List-Post: <mailto:list-moderator@example.com?subject=list%20posting> List-Post: NO (posting not allowed on this list) 3.5. List-Owner The List-Owner header field identifies the path to contact a human administrator for the mailing list. The URI may contain the email address of an administrator for the mailing list, the mail system administrator, or any other person who can handle user contact for the mailing list. There is no need to specify List-Owner if it is the same person as the mail system administrator (postmaster). Examples: List-Owner: <mailto:list-admin@example.com> (Contact Person for Help) List-Owner: <mailto:grant@example.com> (Grant Neufeld) List-Owner: <mailto:josh@example.com?Subject=list> 3.6. List-Archive The List-Archive header field describes how to access archives for the mailing list. Examples: Moonesamy Expires June 13, 2012 [Page 9]
Internet-Draft URIs for Core Mailing List Commands December 2011 List-Archive: <mailto:list-request@example.com?subject=index%20list> List-Archive: <ftp://ftp.example.com/pub/list/archive/> List-Archive: <http://www.example.com/list/archive/> (Web Archive) List-Archive: <imap://archive.example.com/list> The Archive-At header field [RFC5064] provides a pointer to an archived form of a single message. 3.7. List-Id The List-Id header field provides an identifier for an e-mail distribution list [RFC2919]. 4. Supporting Nested Lists A mailing list that is a sublist for another mailing list in a nested mailing list hierarchy will need to modify some of the List- header fields, while leaving others as the parent list set them. Sublists SHOULD remove the parent list's List-Help, List-Subscribe, List-Unsubscribe and List-Owner header fields, and SHOULD insert their own versions of those header fields. If the sublist provides its own archive, it SHOULD replace the List- Archive with its own. Otherwise, it MUST leave the List-Archive header field untouched. Dependant on how postings to the mailing list are handled, the sublist MAY replace the List-Post field. The appropriateness of whether to replace List-Post is left to the determination of the individual list administrators. If the intention is that postings should be distributed to all members of the primary mailing list, List-Post should not be changed by a sublist in such a way that postings will be distributed only to members of the sublist. Moonesamy Expires June 13, 2012 [Page 10]
Internet-Draft URIs for Core Mailing List Commands December 2011 5. Security Considerations There are very few new security concerns generated with this proposal. Message headers fields are an existing standard, designed to easily accommodate new types. There may be concern with multiple header fields being inserted or headers fields being forged, but these are problems inherent in Internet mail, not specific to this specification. Furthermore, the implications are relatively harmless. Mailing list managers should not allow any user-originated list header fields to pass through to the mailing lists, lest they confuse the user and have the potential to create security problems. On the client side, there may be some concern with posts or commands being sent in error. It is required that the user have a chance to confirm any action before it is executed. In the case of mailto, it may be appropriate to create the correctly formatted message without sending it, allowing the user to see exactly what is happening and giving the user the opportunity to approve or discard the message before it is sent. All security considerations for the use of URIs [RFC3986] apply equally to this specification. Mail User Agents should not process list header field URIs which could compromise the security of the user's system. This includes the "file://" URI type which could potentially be used to trigger the execution of a local application on some user systems. 6. IANA Considerations The List-Archive, List-Help, List-Owner, List-Post, List-Subscribe, and List-Unsubscribe references in the Permanent Message Header Field Names registry should be updated to point to this document. 7. Acknowledgements Most of the text in this document was copied from RFC 2369, authored by Joshua D. Baer and Grant Neufeld. The numerous participants of the List-Header, ListMom-Talk, List- Managers and MIDA-Mail mailing lists contributed much to the formation and structure of RFC 2369 with Keith Moore and Christopher Allen providing guidance on the standards process. Moonesamy Expires June 13, 2012 [Page 11]
Internet-Draft URIs for Core Mailing List Commands December 2011 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, October 2008. [RFC6068] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto' URI Scheme", RFC 6068, October 2010. 8.2. Informative References [RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND FUNCTIONS", RFC 2142, May 1997. [RFC2369] Neufeld, G. and J. Baer, "The Use of URLs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields", RFC 2369, July 1998. [RFC2919] Chandhok, R. and G. Wenger, "List-Id: A Structured Field and Namespace for the Identification of Mailing Lists", RFC 2919, March 2001. [RFC5064] Duerst, M., "The Archived-At Message Header Field", RFC 5064, December 2007. Appendix A. Appendix A.1. Client Implementation A.1.1. Guidelines For 'mailto' URI based commands, Mail User Agents may choose to provide specialized feedback (such as presenting a dialog or alert), instead of the actual command email message, asking for command confirmation from the user. The feedback should identify the message destination and command within a more descriptive explanation. For example: Moonesamy Expires June 13, 2012 [Page 12]
Internet-Draft URIs for Core Mailing List Commands December 2011 "Do you want to send the unsubscription command 'unsubscribe somelist' to 'somelist-request@some.example.com'? Sending the command will result in your removal from the associated list." If the user has multiple email addresses supported by the Mail User Agent, the MUA should prompt the user for which email address to use when subscribing or performing some other action where the email address to use cannot be specifically determined. When unsubscribing or such, the email address that is subscribed should be used, unless that is not known by the application and cannot be determined from the message headers. A.1.2. Implementation Options The following implementation possibilities are suggested here to give some idea as to why these new header fields will be useful, and how they could be supported. In most cases, it may be helpful to disable the interface for the commands when not applicable to the currently selected message. A.1.2.1. Key combinations and command lines On text based systems which utilize command lines or key combinations, each field could be implemented as a separate command. Thus one combination would subscribe the user, another would unsubscribe, a third request help, etc. The commands would only be available on messages containing the list header fields. A.1.2.2. Menu items On graphical systems which have menus, these commands could take the form of a menu or sub-menu of items. For example, a "Lists" menu might appear when viewing messages containing the header fields, with items named "Subscribe", "Unsubscribe", "Get Help", "Post Message to List", "Contact List Owner" and "Access List Archive". This menu could be disabled when not applicable to the current message or disappear entirely. A.1.2.3. Push Buttons and Pallettes On graphical window systems, buttons could be placed in the window of the message, a toolbar, or in a floating pallette of their own. Each button could correspond to a command, with names "Subscribe", "Unsubscribe", "Get Help", "Post to List", "List Owner" and "Archive". These buttons or pallettes could be disabled when not applicable to the current message or disappear entirely. Moonesamy Expires June 13, 2012 [Page 13]
Internet-Draft URIs for Core Mailing List Commands December 2011 A.1.2.4. Feedback to the User If using a dialog interface (or other feedback element) the mail user agent must include an option for the user to review (and possibly modify) the message before it is sent. It may also be useful for mail user agents to provide a link to more detailed context- sensitive assistance about mailing list access in general. A.2. Changes from RFC 2369 This appendix contains a list of changes between this document and RFC 2369. o URL changed to URI o Replaced MTAs with mailing list managers in the sentence: "MTAs generating the header fields SHOULD". o Replaced MTAs with mailing list managers in the sentence: "MTAs MUST NOT insert whitespace within the brackets" in Section 2 o In Section 2, client application SHOULD ignore whitespace within brackets o Updated references o Added informative references to RFC 2919 and RFC 5064 o Editorial changes o Removed Background Discussion Author's Address S. Moonesamy (editor) 76, Ylang Ylang Avenue Quatre Bornes Mauritius Email: sm+ietf@elandsys.com Moonesamy Expires June 13, 2012 [Page 14]
