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Versions: 00 01 02 03 04 05 06 07 RFC 3458

Network Working Group                                           E. Burger
Internet Draft                                         SnowShore Networks
Document: draft-ietf-vpim-hint-07.txt                          E. Candell
Category: Standards Track                                        Comverse
Expires December 2001                                            C. Eliot
                                                    Microsoft Corporation
                                                                 G. Klyne
                                                   Baltimore Technologies
                                                             June 5, 2001


                   Message Context for Internet Mail

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 [1].

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt .

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html .

   This document is a work product of the IETF Voice Profile for
   Internet Mail (VPIM) Work Group.



1. Abstract

   This memo describes a new RFC2822 message header, "Message-Context".
   This header provides information about the context and presentation
   characteristics of a message.

   A receiving user agent (UA) may use this information as a hint to
   optimally present the message.







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Table of Contents

1. Abstract...........................................................1
2. Introduction.......................................................3
3. Conventions used in this document..................................3
4. Motivation.........................................................4
5. Functional Requirements............................................5
6. Determining the Message Context....................................6
7. Message-Context Reference Field....................................7
7.1. Message-Context Syntax...........................................7
7.2. message-context-class Syntax.....................................7
7.2.1. voice-message..................................................8
7.2.2. fax-message....................................................8
7.2.3. pager-message..................................................8
7.2.4. multimedia-message.............................................8
7.2.5. text-message...................................................8
7.2.6. none...........................................................9
8. Security Considerations............................................9
9. IANA Considerations................................................9
9.1. Message Content Type Registrations..............................10
9.2. Registration Template...........................................10
9.3. Message-Context Registration....................................11
10. APPENDIX: Some messaging scenarios...............................11
10.1. Internet e-mail................................................11
10.2. Pager service..................................................12
10.3. Facsimile......................................................13
10.4. Voice mail.....................................................13
10.5. Multimedia message.............................................13
11. References.......................................................14
12. Acknowledgments..................................................15
13. Author's Addresses...............................................15
14. Full Copyright Statement.........................................17

















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2. Introduction

   This document describes a mechanism to allow senders of an Internet
   mail message to convey the message's contextual information.  Taking
   account of this information, the receiving user agent (UA) can make
   decisions that improve message presentation for the user in the
   context the sender and receiver expects.

   In this document, the "message context" conveys information about
   the way the user expects to interact with the message.  For example,
   a message may be e-mail, voice mail, fax mail, etc.  A smart UA may
   have specialized behavior based on the context of the message.

   This document specifies a RFC2822 header called "Message-Context".
   The mechanism is in some ways similar to the use of the Content-
   Disposition MIME entity described in [2].  Content-Disposition gives
   clues to the receiving User Agent (UA) for how to display a given
   body part.  Message-Context can give clues to the receiving UA for
   the presentation of the message.  This allows the receiving UA to
   present the message in a meaningful and helpful way to the
   recipient.

   Typical uses for this mechanism include:
   o    Selecting a special viewer for a given message.
   o    Selecting an icon indicating the kind of message in a displayed
        list of messages.
   o    Arranging messages in an inbox display.
   o    Filtering messages the UA presents when the user has limited
        access.


3. Conventions used in this document

   This document refers generically to the sender of a message in the
   masculine (he/him/his) and the recipient of the message in the
   feminine (she/her/hers).  This convention is purely for convenience
   and makes no assumption about the gender of a message sender or
   recipient.

   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 RFC-2119 [3].

   FORMATTING NOTE: Notes, such at this one, provide additional
   nonessential information that the reader may skip without missing
   anything essential.  The primary purpose of these non-essential
   notes is to convey information about the rationale of this document,
   or to place this document in the proper historical or evolutionary
   context.  Readers whose sole purpose is to construct a conformant
   implementation may skip such information.  However, it may be of use
   to those who wish to understand why we made certain design choices.


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4. Motivation

   Multimedia messaging systems receive messages that a UA may present
   in variety of ways.  For example, traditional e-mail uses simple
   text messages that the recipient displays and edits.  One UA may
   automatically print Fax images.  Another UA may play voice messages
   through a telephone handset.  Likewise, a receiving desktop computer
   may process or present documents transferred over e-mail using a
   local application.  Emerging and future developments may deliver
   other forms of information that have their own characteristics for
   user presentation, such as video messages and pager messages.

   An often-requested characteristic for multimedia messaging systems
   is to collect received messages in a "universal inbox", and to offer
   them to the user as a combined list.

   In the context of "unified messaging", different message contexts
   may have different implied semantics.  For example, some users may
   perceive voicemail to have an implicit assumption of urgency.  Thus
   they may wish to gather them together and process them before other
   messages.  This results in the end-user receiving agent needing to
   be able to identify voicemail and distinguish it from other
   messages.

   The uses of this kind of presentation characteristic for each
   message is multi-fold:

   o    Display an indication to the user (e.g., by a suitably
        evocative icon along with other summary fields),

   o    Auto-forward a given message type into another messaging
        environment (e.g., a page to a mobile short message service),

   o    Prioritize and group messages in an inbox display list,

   o    Suggest appropriate default handling for presentation,

   o    Suggest appropriate default handling for reply, forward, etc.,
        and

   A problem faced by multimedia messaging systems is that it is not
   always easy to decide the context of a received message.  For
   example, consider the following scenarios.

   o    A message that contains audio and image data:  Is this a fax
        message that happens to have some voice commentary?  Is it a
        voice message that is accompanied by some supplementary
        diagrams?  Is it a fully multimedia message, in which all parts
        are expected to carry equal significance?



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   o    A message containing text and audio data:  Is this e-mail with
        an MP3 music attachment?  Is it a voice message that happens to
        have been generated with an initial text header for the benefit
        of non-voice-enabled e-mail receivers?

   The message context does relate to the message media content.
   However, it is not the same thing.  As shown above, the media type
   used in a message is not sufficient to indicate the message context.
   One cannot determine a priori which media types to use in
   alternative (gateway) message.  Also, what if the user cares about
   distinguishing traditional e-mail text from SMS messages?  They are
   both the same media type, text, but they have different user
   contexts.


5. Functional Requirements

   The goals stated above lead to the following functional
   requirements.

   For receivers:
   o    Identify a message as belonging to a message class.

   o    Incorrect or invalid message classification must not result in
        failure to transfer or inability to present a message.


   For senders:
   o    Specify message classes by the originating user's choice of
        authoring tool or simple user interaction.


   For both:
   o    Specify a well-defined set of message classes to make
        interoperability between mail user agents (UAs) possible.

   o    Message classification information has to be interpretable in
        reasonable fashion by many different user agent systems.

   o    The mechanism should be extensible to allow for the
        introduction of new kinds of messages.

   NOTE: We specifically do not specify user agent behavior when the
   user agent forwards a message.  Clearly, the user agent, being
   message-context-aware, should provide a meaningful message-context.
   It is obvious what to do for the easy cases.  Messages that the user
   simply forwards will most likely keep the context unchanged.
   However, it is beyond the scope of this document to specify the user
   agent behavior for any other scenario.




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6. Determining the Message Context

   One method of indicating the interpretation context of a message is
   to examine the media types in the message.  However, this requires
   the UA to scan the entire message before it can make this
   determination.  This approach is particularly burdensome for the
   multi-media mail situation, as voice and especially video mail
   objects are quite large.

   We considered indicating the message context by registering a
   multipart/* MIME subtype (Content-Type).  For example, the VPIM Work
   Group has registered multipart/voice-message to indicate that a
   message is primarily voice mail [4].  However, multipart/voice-
   message is identical in syntax to multipart/mixed.  The only
   difference is that VPIM mail transfer agents and user agents
   recognize that they can perform special handling of the message
   based on it being a voice mail message.  Moreover, Content-Type
   refers to a given MIME body part, not to the message as a whole.

   We wish to avoid scanning the entire message.  In addition, we wish
   to avoid having to create multiple aliases for multipart/mixed every
   time someone identifies a new primary content type.  Multiple
   aliases for multipart/mixed are not desirable as they remove the
   possibility for specifying a message as multipart/alternate,
   multipart/parallel, or multipart/encrypted, for example.

   Since the message context is an attribute of the entire message, it
   is logical to define a new top-level (RFC2822 [5]) message
   attribute.  To this end, this document introduces the message
   attribute "Message-Context".

   Message-Context only serves to identify the message context.  It
   does not provide any indication of content that the UA must be
   capable of delivering.  It does not imply any message disposition or
   delivery notification.  There is a related effort to define Critical
   Content of Internet Mail [6] that one might use to perform these
   tasks.

   Message-Context is only an indicator.  We do not intend for it to
   convey information that is critical for presentation of the message.
   One can conceive of goofy situations, such as a message marked
   "voice-message" but without an audio body part.  In this case, the
   fact that the contents of a message donÆt match its context does not
   mean the receiving system should generate an error report or fail to
   deliver or process the message.








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7. Message-Context Reference Field

   The Message-Context reference field is a top-level header inserted
   by the sending UA to indicate the context of the message.

   A receiving user agent MUST NOT depend on the indicated message-
   context value in a way that prevents proper presentation of the
   message.  If the value is incorrect or does not match the message
   content, the receiving user agent MUST still be capable of
   displaying the message content at least as meaningfully as it would
   if no Message-Context value were present.

   One can envision situations where a well-formed message ends up not
   including a media type one would expect from the message-context.
   For example, consider a voice messaging system that records a voice
   message and also performs speech-to-text processing on the message.
   The message then passes through a content gateway, such as a
   firewall, that removes non-critical body parts over a certain
   length.  The receiving user agent will receive a message in the
   voice-message context that has only a text part and no audio.  Even
   though the message does not have audio, it is still in the voice
   message context.

   Said differently, the receiving UA can use the message-context to
   determine whether, when, and possibly where to display a message.
   However, the message-context should not affect the actual rendering
   or presentation.  For example, if the message is in the voice-
   message context, then don't try to send it to a fax terminal.
   Conversely, consider the case of a message in the voice-message
   context that gets delivered to a multimedia voice terminal with a
   printer.  However, this message only has fax content.  In this
   situation, the "voice-message" context should not stop the terminal
   from being properly rendering the message.


7.1. Message-Context Syntax

   The syntax of the Message-Context field, described using the ABNF
   [7] is as follows.  Note that the Message-Context header field name
   and message-context-class values are not case sensitive.

        "Message-Context" ":" message-context-class CRLF

7.2. message-context-class Syntax

   The message-context-class indicates the context of the message.
   This is an IANA registered value.  Current values for message-
   context-class are as follows.





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        message-context-class =  (   "voice-message"
                                   | "fax-message"
                                   | "pager-message"
                                   | "multimedia-message"
                                   | "text-message"
                                   | "none"
                                   | extension-type )

        extension-type = token  ; Defined and registered per Section 8
                       / vnd.token ; Experimental, private use

        token = <syntax as defined by [8],
                 but not starting with the characters "vnd.">

        vnd.token = <Vendor-specific, private token>

   Note: The values for Message-Context must be either IANA registered
   values or experimental, vendor tokens.  This ensures that user
   agents from different vendors will interoperate and perform in a
   uniform manner without an undue burden on the vendors.

7.2.1. voice-message

   The voice-message class states the message is a voice mail message.

7.2.2. fax-message

   The fax-message class states the message is a facsimile mail
   message.

7.2.3. pager-message

   The pager-message class states the message is a page, such as a text
   or numeric pager message or a traditional short text message service
   (SMS) message.

7.2.4. multimedia-message

   The multimedia-message class states the message is an aggregate
   multimedia message, such as a message specified by [9].  This helps
   identify a message in a multimedia context.  For example, a MIME
   multipart/related [10] data part and resource part looks the same as
   a multimedia MHTML multipart/related.  However, the semantics are
   quite different.

7.2.5. text-message

   The text-message class states the message is a traditional internet
   mail message.  Such a message consists of text, possibly richly
   formatted, with or without attachments.



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7.2.6. none

   The none class states there is no context information for this
   message.

   If a message has no Message-Context reference field, a receiving
   user agent MUST treat it the same as it would if the message has a
   "none" value.


8. Security Considerations
   The intention for this header is to be an indicator only of message
   context.  One can imagine someone creating an "Application" Message-
   Context.  A poorly designed user agent could blindly execute a
   mailed program based on the Message-Context.  Don't do that!

   One can envision a denial of service attack by bombing a receiver
   with a message that has a Message-Context that doesn't fit the
   profile of the actual body parts.  This is why the receiver
   considers the Message-Context to be a hint only.


9. IANA Considerations

   Section 9.3 is a registration for a new top-level RFC2822 [5]
   message header, "Message-Context".

   This document creates an extensible set of context types.  To
   promote interoperability and coherent interpretations of different
   types, we need a central repository for well-known context types.

   IANA will create a repository for context types called "Internet
   Message Context Types".  Following the policies outlined in [11],
   this repository is "Specification Required" by RFC.  Section 9.1
   describes the initial values for this registry.

   To create a new message context type, you MUST publish an RFC to
   document the type.  In the RFC, include a copy of the registration
   template found in Section 9.2 of this document.  Put the template in
   your IANA Considerations section, filling-in the appropriate fields.
   You MUST describe any interoperability and security issues in your
   draft.











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9.1. Message Content Type Registrations

   Internet Message Content Types
   ==============================

   Value              Description                           Reference
   -----              -----------                           ---------
   voice-message      Indicates a message whose primary     This RFC
                      content is a voice mail message.  The
                      primary content is audio data.  The
                      context is usually a message recorded
                      from a voice telephone call.

   fax-message        Indicates a message whose primary     This RFC
                      content is a fax mail message.  The
                      primary content is image data.  The
                      context is usually a message recorded
                      from a facsimile telephone call.

   pager-message      Indicates a message whose primary     This RFC
                      content is a page.  The primary
                      content is text data.  The context is
                      an urgent message usually of a
                      limited length.

   multimedia-message Indicates a message whose primary     This RFC
                      content is a multimedia message.  The
                      primary content is multimedia, most
                      likely MHTML.  The context is often
                      spam or newsletters.

   text-message       Indicates a classic, text-based,      This RFC
                      Internet message.

   None               Indicates an unknown message context. This RFC


9.2. Registration Template

   In the following template, a pipe symbol, "|", precedes instructions
   or other helpful material.  Be sure to replace "<classname>" with
   the class name you are defining.


   Message-Context class name:
   <classname>

   Summary of the message class:
       | Include a short (no longer than 4 lines) description or summary
       | Examples:
       |   "Palmtop devices have a 320x160 pixel display, so we can..."
       |   "Color fax is so different than black & white that..."

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   Person & email address to contact for further information:
       | Name & e-mail


9.3. Message-Context Registration

   To: iana@iana.org
   Subject: Registration of New RFC 2822 Header

   RFC 2822 Header Name:
   Message-Context

   Allowable values for this parameter:
   Please create a new registry for Primary Context Class
   registrations.  See section 9.1 of this document for the initial
   values.

   RFC 2822 Section 3.6 Repeat Value:
   Field             Min Number   Max Number   Notes
   Message-Context       0            1

   Person & email address to contact for further information:
   Eric Burger
   e.burger@ieee.org


10. APPENDIX: Some messaging scenarios

   This section is not a normative part of this document.  We include
   it here as a historical perspective on the issue of multimedia
   message types.

   These scenarios are neither comprehensive nor fixed.  For example,
   e-mails being typically text-based do not mean that they cannot
   convey a voice-message.  This very mutability serves to underline
   the desirability of providing some explicit message context hint.

10.1. Internet e-mail

   Internet e-mail carries textual information.  Sometimes it conveys
   computer application data of arbitrary size.

   Typically, one uses e-mail for non-urgent messages, which the
   recipient will retrieve and process at a time convenient to her.

   The normal device for receiving and processing e-mail messages is
   some kind of personal computer.  Modern personal computers usually
   come with a reasonably large display and an alphanumeric keyboard.
   Audio, video, and printing capabilities are not necessarily
   available.


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   One can use E-mail for communication between two parties (one-to-
   one), a small number of known parties (one-to-few) or, via an e-mail
   distribution list, between larger numbers of unknown parties (one-
   to-many).

   One of the endearing characteristics of e-mail is the way that it
   allows the recipient to forward all or part of the message a to
   another party, with or without additional comments.  It is quite
   common for an e-mail to contain snippets of content from several
   previous messages. Similar features apply when replying to e-mail.

10.2. Pager service

   One uses a pager message to convey notifications and alerts.  For
   the most part, these notifications are textual information of
   limited size.  The typical limit is 160 characters.  People use
   pages for relatively urgent messages, which the sender wishes the
   receiver to see and possibly respond to within a short time period.
   Pager messages are often used as a way of alerting users to
   something needing their attention.  For example, a system can use a
   page to notify a subscriber there is a voicemail message requiring
   her attention.

   Example devices for sending and receiving a pager message are a
   mobile telephone with a small character display or a text pager.
   Personal computers and personal digital assistants (PDAs) can also
   participate in pager messaging.

   Currently, the most common use of pager messages are between just
   two parties (one-to-one).

   One delivery method for pager messages is the short text messaging
   service (SMS).  SMS is a facility that has evolved for use with
   mobile telephones, and has an associated per-message transmission
   charge.  Note that the focus here is on the notification aspect of
   SMS.  From the beginning, SMS was envisioned to be more than a
   simple pager service.  Operators can use SMS to provision the phone,
   for example.  From the subscriber point of view, SMS has evolved
   considerably from its origins as a pure pager replacement service.
   For example, with mobile originate service, people can have two-way
   text chat sessions using SMS and a mobile phone.  In addition, there
   are SMS-enabled handsets that can display pictures.  However, for
   the purposes of this document, there is still a need to capture the
   essence of a "highly urgent, short-text, notification or alert"
   service.

   Users often send pager messages in isolation, rather than as part of
   a longer exchange.  One use for them is as a prompt or invitation to
   communicate by some more convenient and content-rich method, such as
   a telephone call.



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10.3. Facsimile

   People use facsimile to convey image information of moderate size,
   typically a small number of pages.  Sometimes people use facsimile
   for larger documents.

   Facsimile is a facility that usually uses circuit-switched telephone
   circuits, with connection-time charges.  Message transfer takes
   place in real-time.  Thus, people often use facsimile for urgent
   communication.

   The normal device for sending and receiving a facsimile is a self-
   contained scanning and printing device connected to a telephone line
   or a desktop computer.

   Most facsimiles are between just two parties (one-to-one).  However,
   a significant portion of facsimile service is broadcast between
   multiple parties (one-to-many).

   Most facsimile exchanges are in isolation, rather than as part of a
   longer exchange.  Facsimile data is typically not suitable for
   further processing by computer.

10.4. Voice mail

   People use voice mail to convey audio information, almost
   exclusively human speech.

   Voice mail is a facility that usually uses circuit-switched
   telephone circuits, with modest connection-time charges, often used
   for moderately urgent messages.  A common use for them is as a
   prompt or invitation to communicate by some more convenient method,
   such as a telephone call. In most, but not all cases, the sender of
   a voice message does not want to send a message at all.  Rather,
   they wished to engage in a real-time conversation.

   The normal device for sending and receiving a voice mail is a
   telephone handset.

   Voice messages are usually sent between just two parties (one-to-
   one).

   Voice mail data is not generally suitable for further processing by
   computer.

10.5. Multimedia message

   We define a multimedia message as a message containing more than one
   basic media type (text, image, audio, video, model, application).

   The following are some characteristics of a multimedia message.


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   In some cases, a multimedia message is just e-mail with an
   attachment that a multimedia display application presents.  For
   example, I can send you an MP3 of something I recorded in my garage
   today.

   In other cases, a multimedia message represents a convergence
   between two or more of the scenarios described above.  For example,
   a voice message with an accompanying diagram or a talking head video
   message is a multimedia message.

   The characteristics will vary somewhat with the intent of the
   sender.  This in turn may affect the user agent or application used
   to render the message.



11. References

   1  Bradner, S., "The Internet Standards Process -- Revision 3", BCP
      9, RFC 2026, October 1996.

   2  Troost, R., Dorner, S., and Moore, K., "Communicating
      Presentation Information in Internet Messages: The Content-
      Disposition Header Field", RFC 2183, New Century Systems,
      QUALCOMM Incorporated, and University of Tennessee, August 1997.

   3  Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.

   4  Vaudreuil, G. and Parsons, G., "VPIM Voice Message MIME Sub-type
      Registration", RFC 2423, Lucent Technologies and Northern
      Telecom, September 1998.

   5  Resnick, P., "Internet Message Format", RFC 2822, Qualcomm, April
      2001.

   6  Burger, E., "Critical Content of Internet Mail", draft-ietf-vpim-
      cc-04.txt, Work in Progress.

   7  Crocker, D. and Overell, P. (Editors), "Augmented BNF for Syntax
      Specifications: ABNF", RFC 2234, Internet Mail Consortium and
      Demon Internet Ltd., November 1997.

   8  Freed, N. and Borenstein, N., "Multipurpose Internet Mail
      Extensions (MIME) Part One: Format of Internet Message Bodies",
      RFC 2045, Innosoft and First Virtual, November 1996.

   9  Palme, J., Hopmann, A., Shelness, N., "MIME Encapsulation of
      Aggregate Documents, such as HTML (MHTML)", RFC 2557, Stockholm
      University/KTH, Microsoft, and Lotus Development Corporation,
      March 1999.


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   10 Levinson, E., "The MIME Multipart/Related Content-type", RFC
      2387, August 1998.

   11 Alvestrand, H. and T. Narten, "Guidelines for Writing an IANA
      Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.



12. Acknowledgments

   Many of the ideas here arose originally from a discussion with Jutta
   Degener.

   We'd also like to thank Keith Moore for helping us tighten-up our
   explanations.

   In the last round, we got some rather good advise from Caleb Clausen
   and Dave Aronson.

   Antti Vaha-Sipila pointed out advances in SMS, while Stuart McRae
   helped distil the essence of the pager service vis a vis SMS.

   We offer an extra special thanks to Greg Vaudreuil for pulling RFC
   2557 out of his hat.



13. Author's Addresses

   Eric Burger
   SnowShore Networks, Inc.
   285 Billerica Rd.
   Chelmsford, MA  01824-4120
   USA

   Phone: +1 978 367 8403
   Fax:   +1 603 457 5944
   Email: e.burger@ieee.org


   Emily Candell
   Comverse Network Systems
   200 Quannapowitt Pkwy.
   Wakefield, MA  01880
   USA

   Phone: +1 781 213 2324
   Email: emily.candell@comverse.com



Burger et. al.             Expires 12/05/01                  [Page 15]

                  Message Context for Internet Mail         June 2001


   Graham Klyne
   Baltimore Technologies Ltd.
   1310 Waterside
   Arlington Business Park
   Theale
   Reading, RG7 4SA
   United Kingdom

   Telephone: +44 118 930 8000
   Facsimile: +44 118 930 9000
   E-mail:    GK@ACM.ORG


   Charles Eliot
   Microsoft Corporation
   One Microsoft Way
   Redmond WA 98052
   USA

   Telephone: +1 425 936 9760
   E-Mail:    charle@Microsoft.com
































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14. Full Copyright Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances
   of licenses to be made available, or the result of an attempt made
   to obtain a general license or permission for the use of such
   proprietary rights by implementers or users of this specification
   can be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

   Copyright (C) 2001 The Internet Society.  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.






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