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RFC 3801

Voice Profile for Internet Mail - version 2 (VPIMv2)

Pages: 55
Group: VPIM
Draft STD
Obsoletes:  24212423
Part 1 of 2 – Pages 1 to 27
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Top   ToC   RFC3801 - Page 1
Network Working Group                                       G. Vaudreuil
Request for Comments: 3801                           Lucent Technologies
Obsoletes: 2421                                               G. Parsons
Category: Standards Track                                Nortel Networks
                                                               June 2004

         Voice Profile for Internet Mail - version 2 (VPIMv2)

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).


   This document specifies a restricted profile of the Internet
   multimedia messaging protocols for use between voice processing
   server platforms.  The profile is referred to as the Voice Profile
   for Internet Mail (VPIM) in this document.  These platforms have
   historically been special-purpose computers and often do not have the
   same facilities normally associated with a traditional Internet
   Email-capable computer.  As a result, VPIM also specifies additional
   functionality, as it is needed.  This profile is intended to specify
   the minimum common set of features to allow interworking between
   conforming systems.

   This document obsoletes RFC 2421 and describes version 2 of the
   profile with greater precision.  No protocol changes were made in
   this revision. A list of changes from RFC 2421 are noted in Appendix
   F.  Appendix A summarizes the protocol profiles of this version of
Top   ToC   RFC3801 - Page 2
Table of Contents

   1.   Introduction...................................................3
        1.1.  Voice Messaging System Limitations.......................3
        1.2.  Design Goals.............................................4
        1.3.  Applicability for VPIM...................................5
   2.   Requirements Language..........................................5
   3.   Protocol Restrictions..........................................6
   4.   Voice Message Interchange Format...............................6
        4.1.  VPIM Message Addressing Formats..........................7
        4.2.  Message Header Fields....................................9
        4.3.  MIME Audio Content Descriptions.........................17
        4.4.  Voice Message Content Types.............................19
        4.5.  Other MIME Contents.....................................23
        4.6.  Delivery Status Notification (DSN)......................25
        4.7.  Message Disposition Notification (MDN)..................26
        4.8.  Forwarded Messages......................................26
        4.9.  Reply Messages..........................................27
   5.   Message Transport Protocol....................................27
        5.1.  Base SMTP Protocol......................................28
        5.2.  SMTP Service Extensions.................................28
        5.3.  ESMTP - SMTP Downgrading................................30
   6.   Directory Address Resolution..................................30
   7.   Management Protocols..........................................30
        7.1.  Network Management......................................31
   8.   Conformance Requirements......................................31
   9.   Security Considerations.......................................32
        9.1.  General Directive.......................................32
        9.2.  Threats and Problems....................................32
        9.3.  Security Techniques.....................................33
   10.  Normative References..........................................33
   11.  Acknowledgments...............................................36
   12.  Appendix A - VPIM Requirements Summary........................37
   13.  Appendix B - Example Voice Messages...........................43
   14.  Appendix C - Example Error Voice Processing Error Codes.......49
   15.  Appendix D - Example Voice Processing Disposition Types.......50
   16.  Appendix E - IANA Registrations...............................50
        16.1.  Voice Content-Disposition Parameter Definition.........51
        16.2.  Multipart/Voice-Message MIME Media Type Definition.....51
   17.  Appendix F - Change History: RFC 2421 (VPIM V2) To This Doc...53
   18.  Authors' Addresses............................................54
   19.  Full Copyright Statement......................................55
Top   ToC   RFC3801 - Page 3
1.  Introduction

   MIME is the Internet multipurpose, multimedia-messaging standard.
   This document explicitly recognizes its capabilities and provides a
   mechanism for the exchange of various messaging technologies,
   primarily voice and facsimile.

   Voice messaging evolved as telephone answering service into a full
   send, receive, and forward messaging paradigm with unique message
   features, semantics and usage patterns.  Voice messaging was
   introduced on special purpose computers that interface to a telephone
   switch and provide call answering and voice messaging services.
   Traditionally, messages sent from one voice messaging system to
   another were transported using analog networking protocols based on
   DTMF signaling and analog voice playback. As the demand for
   networking increases, there was a need for a standard high-quality
   digital protocol to connect these machines.  VPIM has successfully
   demonstrated its usefulness as this new standard.  VPIM is widely
   implemented and is seeing deployment in customer networks.  This
   document clarifies ambiguities found in the earlier specification and
   is consistent with implementation practice.  The profile is referred
   to as Voice Profile for Internet Mail (VPIM) in this document.

   This document specifies a restricted profile of the Internet
   multimedia messaging protocols for use between voice processing
   server platforms. These platforms have historically been special-
   purpose computers and often do not have the same facilities normally
   associated with a traditional Internet Email-capable computer.  As a
   result, VPIM also specifies additional functionality, as it is
   needed.  This profile is intended to specify the minimum common set
   of features to allow interworking between conforming systems.

   This document obsoletes RFC 2421 and describes VPIM version 2 of with
   greater precision.  No protocol changes were made in this revision.
   A list of changes from RFC 2421 are noted in Appendix F.  Appendix A
   summarizes the protocol profiles of this version of VPIM.

1.1.  Voice Messaging System Limitations

   The following are typical limitations of voice messaging platforms
   that were considered in creating this baseline profile.

      1) Text messages are not normally received and often cannot be
      easily displayed or viewed.  They can often be processed only via
      text-to-speech or text-to-fax features not currently present in
      many of these machines.
Top   ToC   RFC3801 - Page 4
      2) Voice mail machines usually act as an integrated Message
      Transfer Agent, Message Store and User Agent.  There is typically
      no relaying of messages.  RFC822 header fields may have limited
      use in the context of the limited messaging features currently

      3) Voice mail message stores are generally not capable of
      preserving the full semantics of an Internet message.  As such,
      use of a voice mail machine for gatewaying is not supported.  In
      particular, storage of recipient lists, "Received:" lines, and
      "Message-ID:" may be limited.

      4) Internet-style distribution/exploder mailing lists are not
      typically supported.  Voice mail machines often implement only
      local alias lists, with error-to-sender and reply-to-sender
      behavior. Reply-all capabilities using a Cc list are not generally

      5) Error reports must be machine-parsable so that helpful
      responses can be voiced to users whose only access mechanism is a

      6) The voice mail systems generally limit address entry to 16 or
      fewer numeric characters, and normally do not support alphanumeric
      mailbox names.  Alpha characters are not generally used for
      mailbox identification, as they cannot be easily entered from a
      telephone terminal.

   It should be noted that newer systems are based natively on SMTP/MIME
   and do not suffer these limitations.  In particular, some systems may
   support media other than voice and fax.

1.2.  Design Goals

   It is a goal of this profile to make as few restrictions and
   additions to the existing Internet mail protocols as possible while
   satisfying the requirements for interoperability with current
   generation voice messaging systems.  This goal is motivated by the
   desire to increase the accessibility to digital messaging by enabling
   the use of proven existing networking software for rapid development.

   This specification is intended for use on a TCP/IP network; however,
   it is possible to use the SMTP protocol suite over other transport
   protocols.  The necessary protocol parameters for such use are
   outside the scope of this document.
Top   ToC   RFC3801 - Page 5
   This profile is intended to be robust enough to be used in an
   environment, such as the global Internet, with installed-base
   gateways that do not understand MIME.  Full functionality, such as
   reliable error messages and binary transport, will require careful
   selection of gateways (e.g., via MX records) to be used as VPIM
   forwarding agents. Nothing in this document precludes use of
   general-purpose MIME email packages to read and compose VPIM
   messages.  While no special configuration is required to receive VPIM
   conforming messages, some may be required to originate conforming

   It is expected that a system administrator who can perform TCP/IP
   network configuration will manage a VPIM messaging system.  When
   using facsimile or multiple voice encodings, it is suggested that the
   system administrator maintain a list of the capabilities of the
   networked mail machines to reduce the sending of undeliverable
   messages due to lack of feature support.  Configuration,
   implementation and management of these directory-listing capabilities
   are local matters.

1.3.  Applicability for VPIM

   VPIM is intended for the exchange of voice messages between
   traditional voice messaging systems and for systems that need to
   interoperate with such systems.  VPIM is intended connect voice-
   messaging systems into special-purpose voice messaging networks.
   VPIM may also be used between message store servers and VPIM-aware
   clients such as web servers, TUI, and GUI clients.  VPIM is not
   intended or optimized for downloading to, or sending from commercial
   email clients.

   Internet Voice Messaging, the subject of a separate standards
   initiative, is intended to enable general-purpose email clients to
   send and receive voice content through general-purpose message stores
   in an interoperable way.  IVM may also be a suitable format for
   downloading voice messages from a VPIM server to a commercial email
   client.  It may also be a suitable format for submission of a voice
   message from a general-purpose client into a VPIM system.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [REQ].
Top   ToC   RFC3801 - Page 6
3.  Protocol Restrictions

   This protocol does not limit the number of recipients per message.
   Where possible, server implementations should not restrict the number
   of recipients in a single message.  It is recognized that no
   implementation supports unlimited recipients, and that the number of
   supported recipients may be quite low.

   This protocol does not limit the maximum message length.
   Implementers should understand that some machines will be unable to
   accept excessively long messages.  A mechanism is defined in [SIZE]
   to declare the maximum message size supported.

   The following sections describe the restrictions and additions to
   Internet mail protocols that are required to be conforming with this
   VPIM v2 profile.  Though various SMTP, ESMTP and MIME features are
   described here, the implementer is referred to the relevant RFCs for
   complete details.  The table in Appendix A summarizes the protocol
   details of this profile.

4.  Voice Message Interchange Format

   The voice message interchange format is a profile of the Internet
   Mail Protocol Suite.  Any Internet Mail message containing the format
   defined in this section is referred to as a VPIM Message in this
   document.  As a result, this document assumes an understanding of the
   Internet Mail specifications.  Specifically, VPIM references
   components from the message format standard for Internet messages
   [RFC822], the Multipurpose Internet Message Extensions [MIME1-5], the
   X.400 gateway specification [X.400], and the delivery status and
   message disposition notifications [REPORT][DSN][DRPT][STATUS][MDN].

   MIME, introduced in [MIME1], is a general-purpose message body format
   that is extensible to carry a wide range of body parts.  It provides
   for encoding binary data so that it can be transported over the 7-bit
   text-oriented SMTP protocol.  This transport encoding (denoted by the
   "Content-Transfer-Encoding:" MIME field) is in addition to the audio
   encoding required to generate a binary object.

   MIME defines two transport-encoding mechanisms to transform binary
   data into a 7-bit representation, one designed for text-like data
   ("Quoted-Printable"), and one for arbitrary binary data ("Base64").
   While Base64 is dramatically more efficient for audio data, either
   will work.  Where binary transport is available, no transport
   encoding is needed, and the data can be labeled as "Binary".
Top   ToC   RFC3801 - Page 7
4.1.  VPIM Message Addressing Formats

   VPIM addresses SHALL use the RFC 822 format based on the Domain Name
   System.  This naming system has two components: the local part, used
   for username or mailbox identification; and the host part, used for
   global machine identification.

4.1.1.  VPIM Addresses

   The local part of the address shall be a US-ASCII string uniquely
   identifying a mailbox on a destination system.  For voice messaging,
   the local part SHALL be a printable string containing the mailbox ID
   of the originator or recipient.  While alpha characters and long
   mailbox identifiers MAY be permitted, short numeric local parts
   SHOULD be used as most voice mail networks rely on numeric mailbox
   identifiers to retain compatibility with the limited 10-digit
   telephone keypad.  As a result, some voice messaging systems may only
   be able to handle a numeric local part.  The reception of
   alphanumeric local parts on these systems may result in the address
   being mapped to some locally unique (but confusing to the recipient)
   number or, in the worst case the address could be deleted making the
   message unreplyable.  Additionally, it may be difficult to create
   messages on these systems with an alphanumeric local part without
   complex key sequences or some form of directory lookup (see 6).  The
   use of the Domain Name System should be transparent to the user.  It
   is the responsibility of the voice mail machine to lookup the fully-
   qualified domain name (FQDN) based on the address entered by the user
   (see 6).

   In the absence of a global directory, specification of the local part
   is expected to conform to international or private telephone
   numbering plans.  It is likely that private numbering plans will
   prevail and these are left for local definition.  However, it is
   RECOMMENDED that public telephone numbers be noted according to the
   international numbering plan described in [E.164].  The indication
   that the local part is a public telephone number is given by a
   preceding "+" (the "+" would not be entered from a telephone keypad,
   it is added by the system as a flag). Since the primary information
   in the numeric scheme is contained by the digits, other character
   separators (e.g., "-") may be ignored (i.e., to allow parsing of the
   numeric local mailbox) or may be used to recognize distinct portions
   of the telephone number (e.g., country code).  The specification of
   the local part of a VPIM address can be split into the four groups
   described below:

      1) mailbox number
          - for use as a private numbering plan (any number of digits)
          - e.g.,
Top   ToC   RFC3801 - Page 8
      2) mailbox number+extension
          - for use as a private numbering plan with extensions
            any number of digits, use of "+" as separator
          - e.g.,

      3) +international number
          - for international telephone numbers conforming to E.164
            maximum of 15 digits
          - e.g.,

      4) +international number+extension
          - for international telephone numbers conforming to E.164
             maximum of 15 digits, with an extension (e.g., behind a
             PBX) that has a maximum of 15 digits.
          - e.g.,

   Note that this address format is designed to be compatible with
   current usage within the voice messaging industry.  It is not
   compatible with the addressing formats of RFCs 2303-2304.  It is
   expected that as telephony services become more widespread on the
   Internet, these addressing formats will converge.

4.1.2.  Special Addresses

   Special addresses to represent the sender are provided for
   compatibility with the conventions of Internet mail.  These addresses
   do not use numeric local addresses, both to conform to current
   Internet practice and to avoid conflict with existing numeric
   addressing plans. Two special addresses are RESERVED for use as


   By convention, a special mailbox named "postmaster" MUST exist on all
   systems.  This address is used for diagnostics and should be checked
   regularly by the system manager. This mailbox is particularly likely
   to receive text messages, which is not normal on a voice-processing
   platform.  The specific handling of these messages is an individual
   implementation choice.


   If a reply to a message is not possible, such as a telephone-
   answering message, then the special address "non-mail-user" SHOULD be
   used as the originator's address.  Any text name such as "Telephone
   Answering", or the telephone number if it is available, is permitted.
   This special address is used as a token to indicate an unreachable
   originator. A conforming implementation MUST NOT permit a reply to an
Top   ToC   RFC3801 - Page 9
   address from "non-mail-user".  For compatibility with the installed
   base of mail user agents, implementations MUST reject the message
   when a message addressed to "non-mail-user" is received.  The status
   code for such NDN's is 5.1.1 "Mailbox does not exist".


          From: Telephone Answering <>

4.1.3.  Distribution Lists

   There are many ways to handle distribution list (DL) expansions and
   none are 'standard'.  A VPIM implementation MAY support DLs.  Using a
   simple alias is a behavior closest to what many voice mail systems do
   today and what is to be used with VPIM messages.  A couple of
   important features that need special care when DLs are used are:

      Reply to the originator - (Address in the RFC822 "Reply-To:" or
                                 "From" field)
      Errors to the submitter - (Address in the MAIL FROM field of the
                                 ESMTP exchange or the "Return-Path:"
                                 RFC822 field)

   Some proprietary voice messaging protocols include only the recipient
   of the particular copy in the envelope and include no "header fields"
   except date and per-message features.  Most voice messaging systems
   do not provide for "Header Information" in their messaging queues and
   only include delivery information.  As a result, recipient
   information MAY be in either the "To:" or "Cc:" header fields. If all
   recipients cannot be presented then the recipient header fields
   SHOULD be omitted to indicate that an accurate list of recipients
   (e.g., for use with a reply-all capability) is not known.

4.2.  Message Header Fields

   Internet messages contain a header information block.  This header
   block contains information required to identify the sender, the list
   of recipients, the message send time, and other information intended
   for user presentation.  Except for specialized gateway and mailing
   list cases, header fields do not indicate delivery options for the
   transport of messages.

   Distribution list processors are noted for modifying or adding to the
   header fields of messages that pass through them.  VPIM systems MUST
   be able to accept and ignore header fields that are not defined here.

   The following header lines are permitted for use with VPIM messages:
Top   ToC   RFC3801 - Page 10
4.2.1.  From


   The originator's fully qualified domain address (a mailbox address
   followed by the fully qualified domain name) MUST be present.
   Systems conforming with this profile SHOULD provide the text personal
   name of the voice message originator in a quoted phrase, if the name
   is available.  Text names of corporate or positional mailboxes MAY be
   provided as a simple string.  From: [RFC822]


               From: "Joe S. User" <>

               From: Technical Support <>


   Voice mail machines may not be able to support separate attributes
   for the "From:" header fields and the SMTP MAIL FROM, VPIM-conforming
   systems SHOULD set these values to the same address.  Use of
   addresses different than those present in the "From:" header field
   address may result in unanticipated behavior.


   The user listed in the "From:" field MUST be presented in the voice
   message envelope of the voice messaging system as the originator of
   the message, though the exact presentation is an implementation
   decision (e.g., the mailbox ID or the text name MAY be presented).
   The "From:" address SHOULD be used for replies (see 4.9).

4.2.2.  To

   The "To:" field contains the recipient's fully-qualified domain




   There MAY be one or more "To:" fields in any message.  Systems SHOULD
   provide a list of recipients only if all recipients are available.
Top   ToC   RFC3801 - Page 11
   Systems, such as gateways from protocols or legacy platforms that do
   not indicate the complete list of recipients, MAY provide a "To:"
   line. Because these systems cannot accurately enumerate all
   recipients in the "To:" headers, recipients SHOULD NOT be enumerated.


   Systems conforming to this profile MAY discard the addresses in the
   "To:" fields if they are unable to store the information.  This
   would, of course, make a reply-to-all capability impossible.  If
   present, the addresses in the "To:" field MAY be used for a reply
   message to all recipients.

4.2.3.  Cc

   The "Cc:" field contains additional recipients' fully qualified
   domain addresses.  Many voice mail systems maintain only sufficient
   envelope information for message delivery and are not capable of
   storing or providing a complete list of additional recipients.


   Conforming implementations MAY send "Cc:" lists if all recipients are
   known at the time of origination.  If not, systems SHOULD omit the
   "Cc:" fields to indicate that the full list of recipients is unknown
   or otherwise unavailable.  The list of disclosed recipients MUST NOT
   include undisclosed recipients (i.e., those sent via a blind copy).




   Systems conforming to this profile MAY add all the addresses in the
   "Cc:" field to the "To:" field, others MAY discard the addresses in
   the "Cc:" fields.  If a list of "Cc:" addresses is present, these
   addresses MAY be used for a reply message to all recipients.

4.2.4.  Date

   The "Date:" field contains the date and time the message was sent by
   the originator.


   The sending system MUST report the time the message was sent.  The
   time zone MUST be present and SHOULD be represented in a four-digit
Top   ToC   RFC3801 - Page 12
   time zone offset, such as -0500 for North American Eastern Standard
   Time.  This MAY be supplemented by a time zone name in parentheses,
   e.g., "-0700 (PDT)".


               Date: Wed, 28 Jul 96 10:08:49 -0800 (PST)

   If the VPIM sender is relaying a message from a system that does not
   provide a time stamp, the time of arrival at the gateway system
   SHOULD be used as the date.


   Conforming implementations SHOULD be able to convert [RFC822] date
   and time stamps into local time

4.2.5.  Sender

   The "Sender:" field contains the actual address of the originator if
   an agent on behalf of the author indicated in the "From:" field sends
   the message.


   This header field MAY be sent by VPIM-conforming systems.


   If the address in the "Sender:" field cannot be preserved in the
   recipient's message queues or in the next-hop protocol from a
   gateway, the field MAY be silently discarded.

4.2.6.  Return-Path

   The "Return-path:" field is added by the final delivering SMTP
   server. If present, it contains the address from the MAIL FROM
   parameter of the ESMTP exchange (see [RFC822]).  Any error messages
   resulting from the delivery failure MUST be sent to this address.
   Note that if the "Return-path:" is null ("<>") (e.g., a call answer
   message would have no return path) delivery status notifications MUST
   NOT be sent.


   The originating system MUST NOT add this header.
Top   ToC   RFC3801 - Page 13

   If the receiving system is incapable of storing the return path (or
   MAIL FROM) to be used for subsequent delivery errors (i.e., it is a
   gateway to a legacy system or protocol), the receiving system must
   otherwise ensure that further delivery errors don't happen.  Systems
   that do not support the return path MUST ensure that at the time the
   message is acknowledged (i.e., when a DSN would be sent), the message
   is delivered to the recipient's ultimate mailbox.  Non-Delivery
   notifications SHOULD NOT be sent after that final delivery.

4.2.7.  Message-id

   The "Message-Id:" field contains a globally unique per-message


   A globally unique message-id MUST be generated for each message sent
   from a VPIM-conforming implementation.


               Message-Id: <>


   When provided in the original message, it MUST be used when sending a
   MDN.  This identifier MAY be used for tracking and auditing.  From

4.2.8.  Reply-To

   If present, the "Reply-To:" header provides a preferred address to
   which reply messages should be sent (see 4.9).  Typically, voice mail
   systems can only support one originator of a message so it is likely
   that this field will be ignored by the receiving system.  From:


   A conforming system SHOULD NOT send a "Reply-To:" header.


   If a "Reply-To:" field is present, a reply-to-sender message MAY be
   sent to the address specified (that is, in lieu of the address in the
   "From:" field).  If the receiving system (e.g., multi-protocol
Top   ToC   RFC3801 - Page 14
   gateway) only supports one address for the originator, then the
   address in the "From:" field MUST be used and the "Reply-To:" field
   MAY be silently discarded.

4.2.9.  Received

   The "Received:" field contains trace information added to the
   beginning of a RFC822 message by MTAs.  This is the only field that
   may be added by an MTA.  Information in this header is useful for
   debugging when using an US-ASCII message reader or a header-parsing
   tool.  From: [RFC822]


   A VPIM-conforming system MUST add a "Received:" field.  When acting
   as a gateway, information about the system from which the message was
   received SHOULD be included.


   A VPIM-conforming system MUST NOT remove any "Received:" fields when
   relaying messages to other MTAs or gateways.  These header fields MAY
   be ignored or deleted when the message is received at the final

4.2.10.  MIME Version

   The "MIME-Version:" field MUST be present to indicate that the
   message conforms to [MIME1-5].  Systems conforming with this
   specification SHOULD include a comment with the words "(Voice 2.0)".
   [VPIM1] defines an earlier version of this profile and uses the token
   (Voice 1.0). Example:

               MIME-Version: 1.0 (Voice 2.0)

   This identifier is intended for information only and SHOULD NOT be
   used to semantically identify the message as being a VPIM message.
   Instead, the presence of the multipart/voice-message content type
   defined in section 18.2 SHOULD be used if identification is

4.2.11.  Content-Type

   The "Content-Type:" header MUST be present to declare the type of
   content enclosed in the message.  The typical top-level content in a
   VPIM Message SHOULD be Multipart/Voice-Message.  The allowable
   contents are detailed starting in section 4.4 of this document.
   From: [MIME2]
Top   ToC   RFC3801 - Page 15
4.2.12.  Content-Transfer-Encoding

   Because Internet mail was initially specified to carry only 7-bit
   US-ASCII text, it may be necessary to encode voice and fax data into
   a representation suitable for that environment.  The "Content-
   Transfer-Encoding:" header describes this transformation if it is


   An implementation in conformance with this profile SHOULD send audio
   and/or facsimile data in "Binary" form when binary message transport
   is available (see section 5).  When binary transport is not
   available, implementations MUST encode the audio and/or facsimile
   data as "Base64".


   Conforming implementations MUST recognize and decode the standard
   encodings, "Binary" (when binary support is available), "7bit,
   "8bit", "Base64" and "Quoted-Printable" per [MIME1].  The detection
   and decoding of "Quoted-Printable", "7bit", and "8bit" MUST be
   supported in order to meet MIME requirements and to preserve
   interoperability with the fullest range of possible devices.

4.2.13.  Sensitivity

   The "Sensitivity:" field, if present, indicates the requested privacy
   level.  If no privacy is requested, this field is omitted.  The
   header definition is as follows:

   Sensitivity := "Sensitivity" ":" Sensitivity-value

   Sensitivity-value := "Personal" / "Private" / "Company-Confidential"


   A VPIM-conforming implementation MAY include this header to indicate
   the sensitivity of a message.  If a user marks a message "Private", a
   conforming implementation MUST send only the "Private" sensitivity
   level.  There are no VPIM-specific semantics defined for the values
   "Personal" or "Company-Confidential".  A conforming implementation
   SHOULD NOT send the values "Personal" or "Company-Confidential".  If
   the message is of "Normal" sensitivity, this field SHOULD be omitted.
   From: [X.400]
Top   ToC   RFC3801 - Page 16

   If a "Sensitivity:" field with a value of "Private" is present in the
   message, a conforming system MUST prohibit the recipient from
   forwarding this message to any other user.  A conforming system,
   however, SHOULD allow the responder to reply to a sensitive message,
   but SHOULD NOT include the original message content.  The responder
   MAY set the sensitivity of the reply message.

   A receiving system MAY ignore sensitivity values of "Personal" and
   "Company Confidential".

   If the receiving system does not support privacy and the sensitivity
   is "Private", a negative delivery status notification MUST be sent to
   the originator with the appropriate status code (5.6.0) "Other or
   undefined protocol status" indicating that privacy could not be
   assured.  The message contents SHOULD be returned to the sender to
   allow for a voice context with the notification.  A non-delivery
   notification to a private message SHOULD NOT be tagged private since
   it will be sent to the originator.  From: [X.400]

   A message with no privacy explicitly noted (i.e., no header) or with
   "Normal" sensitivity has no special treatment.

4.2.14.  Importance

   Indicates the requested importance to be given by the receiving
   system. If no special importance is requested, this header MAY be
   omitted and the value of the absent header assumed to be "normal".
   From: [X.400]

   Importance := "Importance" ":" importance-value

   Importance-value := "low" / "normal" / "high"


   Conforming implementations MAY include this header to indicate the
   importance of a message.


   If the receiving system does not support "Importance:", the attribute
   MAY be silently dropped.
Top   ToC   RFC3801 - Page 17
4.2.15.  Subject

   The "Subject:" field is often provided by email systems but is not
   widely supported on voice mail platforms.  From: [RFC822]


   For compatibility with text-based mailbox interfaces, a text subject
   field SHOULD be generated by a conforming implementation.  It is
   RECOMMENDED that voice-messaging systems that do not support any text
   user interfaces (e.g., access only by a telephone) insert a generic
   subject header of "VPIM Message" or "Voice Message" for the benefit
   of GUI-enabled recipients.


   It is anticipated that many voice-only systems will be incapable of
   storing the subject line.  The subject MAY be discarded by a
   receiving system.

4.3.  MIME Audio Content Descriptions

4.3.1.  Content-Description

   This field MAY be present to facilitate the text identification of
   these body parts in simple email readers.  Any values may be used.


         Content-Description: Big Telco Voice Message


   This field MAY be added to a voice body part to offer a freeform
   description of the voice content.  It is useful to incorporate the
   values for Content-Disposition with additional descriptions.  For
   example, this can be used to indicate product name or transcoding


   This field MAY be displayed to the recipient.  However, since it is
   only informative it MAY be ignored.
Top   ToC   RFC3801 - Page 18
4.3.2.  Content-Disposition

   This field MUST be present to allow the parsable identification of
   body parts within a VPIM voice message.  This is especially useful
   if, as is typical, more than one Audio/* body occurs within a single
   level (e.g., Multipart/Voice-Message).  Since a VPIM voice message is
   intended to be automatically played in the order in which the audio
   contents occur, the audio contents MUST always be of disposition
   inline.  However, it is still useful to include a filename value, so
   this SHOULD be present if this information is available.  From:


   In order to distinguish between the various types of audio contents
   in a VPIM voice message a new disposition parameter "voice" is
   defined with IANA (see section 18.1) with the parameter values below
   to be used as appropriate:

   Audio-Type := "voice" "=" Audio-type-value

   Audio-type-value := "Voice-Message" / "Voice-Message-Notification" /
   "Originator-Spoken-Name" /"Recipient-Spoken-Name" /"Spoken-Subject"

      Voice-Message - the primary voice message,
      Voice-Message-Notification - a spoken delivery notification
        or spoken disposition notification,
      Originator-Spoken-Name - the spoken name of the originator,
      Recipient-Spoken-Name - the spoken name of the recipient(s) if
        available to the originator
      Spoken-Subject- the spoken subject of the message, typically
        spoken by the originator

   Note that there SHOULD only be one instance of each of these types of
   audio contents per message level.  Additional instances of a given
   type (i.e., parameter value) MAY occur within an attached forwarded
   or reply voice message.  If there are multiple recipients for a given
   message, recipient-spoken-name MUST NOT be used.


   Implementations SHOULD use this header.  However, those that do not
   understand the "voice" parameter (or the "Content-Disposition:"
   header) can safely ignore it, and will present the audio body parts
   in order (but will not be able to distinguish between them).  If more
   than one instance of the "voice" parameter type value is encountered
   at one level (e.g., multiple 'Voice-Message' tagged contents) then
   they SHOULD be presented together.
Top   ToC   RFC3801 - Page 19
4.3.3.  Content-Duration

   The "Content-Duration:" header provides an indication of the audio
   length in seconds of the segment.


         Content-Duration: 33


   This field MAY be present to allow the specification of the length of
   the audio body part in seconds.


   The use of this field on reception is a local implementation issue.
   From: [DUR]

4.3.4.  Content-Language:

   This field MAY be present to allow the specification of the spoken
   language of the audio body part.  The encoding is defined in [LANG].

   Example for UK English:

         Content-Language: en-UK


   A sending system MAY add this field to indicate the language of the
   voice.  The determination of this (e.g., automated or user-selected)
   is a local implementation issue.


   The use of this field on reception is a local implementation issue.
   It MAY be used as a hint to the recipient (e.g., end-user or an
   automated translation process) as to the language of the voice

4.4.  Voice Message Content Types

   The content types described in this section are identified for use
   within the Multipart/Voice-Message content.  This content is referred
   to as a "VPIM message" in this document and is the fundamental part
   of a "VPIM message".
Top   ToC   RFC3801 - Page 20
   Only the contents profiled can be sent within a VPIM voice message
   construct (i.e., the Multipart/Voice-Message content type) to form a
   simple or a more complex structure (several examples are given in
   Appendix B).  The presence of other contents within a VPIM voice
   message is not permitted. In the absence of a bilateral agreement,
   conforming implementations MUST NOT create a message containing
   prohibited contents.  In the spirit of liberal acceptance, a
   conforming implementation MAY accept and render prohibited content.
   Systems unable to accept or render prohibited contents MAY discard
   the prohibited contents as necessary to deliver the acceptable
   content.  When multiple contents are present within the
   Multipart/Voice-Message, they SHOULD be presented to the user in the
   order that they appear in the message.

   Some deployed implementations based on a common interpretation of the
   original VPIM v2 specification reject messages with prohibited
   content rather than discard the unsupported contents.  For
   interoperability with these systems, it is especially important that
   prohibited contents not be sent within a Multipart/Voice-Message.

4.4.1.  Multipart/Voice-Message

   This MIME multipart structure provides a mechanism for packaging a
   voice message into one container that is tagged as VPIM v2
   conforming.  The sub-type is identical in semantics and syntax to
   multipart/mixed, as defined in [MIME2].  As such, it may be safely
   interpreted as a multipart/mixed by systems that do not understand
   the sub-type (only the identification as a voice message would be

   In addition to the MIME required boundary parameter, a version
   parameter is also required for this sub-type.  This is to distinguish
   this refinement of the sub-type from the previous definition in
   [VPIM1].  The value of the version parameter is "2.0" if the content
   conforms to the requirements of this specification.  Should there be
   further revisions of this content type, there MUST be backwards
   compatibility (i.e., systems implementing version n can read version
   2, and systems implementing version 2 can read version 2 contents
   within a version n).


   The Multipart/Voice-Message content-type MUST only contain the
   profiled media and content types specified in this section (i.e.,
   Audio/*, Image/*, and Message/RFC822).  The most common will be:
   spoken name, spoken subject, the message itself, and an attached fax.
   Forwarded messages are created by simply using the Message/RFC822
Top   ToC   RFC3801 - Page 21
   Conformant implementations MUST use Multipart/Voice-Message in a VPIM
   message.  In most cases, this Multipart/Voice-Message Content-Type
   will be the top level but may be included within a Message/RFC822 if
   the message is forwarded or within a multipart/mixed when more than
   one message is being forwarded.


   Conformant implementations MUST recognize the Multipart/Voice-Message
   content (whether it is a top-level content or contained in a
   Multipart/Mixed) and MUST be able to separate the contents (e.g.,
   spoken name or spoken subject).

   The semantic of Multipart/Voice-Message (defined in section 18.2) is
   identical to Multipart/Mixed and may be interpreted as that by
   systems that do not recognize this content-type.

4.4.2.  Message/RFC822


   MIME requires support of the Message/RFC822 message encapsulation
   body part.  This body part SHOULD be used within a Multipart/Voice-
   Message to forward complete messages (see 4.8) or to reply with
   original content (see 4.9).  From: [MIME2]


   The receiving system MUST accept this format and SHOULD treat this
   attachment as a forwarded message.  The receiving system MAY flatten
   the forwarding structure (i.e., remove this construct to leave
   multiple voice contents or even concatenate the voice contents to fit
   in a recipient's mailbox), if necessary.

4.4.3.  Audio/32KADPCM


   An implementation conforming to this profile MUST send Audio/32KADPCM
   by default for voice [ADPCM].  This encoding is a moderately-
   compressed encoding with a data rate of 32 kbits/second using
   moderate processing resources. Typically, this body contains several
   minutes of message content;  however, if used for spoken name or
   subject the content is expected to be considerably shorter (i.e.,
   about 5 and 10 seconds respectively).
Top   ToC   RFC3801 - Page 22

   Receivers MUST be able to accept and decode Audio/32KADPCM.  If an
   implementation can only handle one voice body, then multiple voice
   bodies (if present) SHOULD be concatenated, and MUST NOT be
   discarded. If concatenated, the contents SHOULD be in the same order
   they appeared in the multipart.

4.4.4.  Image/TIFF

   A common image encoding for facsimile, known as TIFF-F, is a
   derivative of the Tag Image File Format (TIFF) and is described in
   several documents.  For the purposes of VPIM, the F Profile of TIFF
   for Facsimile (TIFF-F) is defined in [TIFF-F], and the Image/TIFF
   MIME content-type is defined in [TIFFREG].  While there are several
   formats of TIFF, only TIFF-F is profiled for use within
   Multipart/Voice-Message. Further, since the TIFF-F file format is
   used in a store-and-forward mode with VPIM, the image MUST be encoded
   so that there is only one image strip per facsimile page.


   All VPIM implementations that support facsimile MUST generate TIFF-F
   compatible facsimile contents in the Image/TIFF subtype using the
   application=faxbw encoding by default.  If the VPIM message is a
   voice- annotated fax, the implementation SHOULD send this fax content
   in Multipart/Voice-Message.  If the message is a simple fax, an
   implementation MAY send it without using the Multipart/Voice-Message
   to be more compatible with fax-only (RFC 2305) implementations.

   While any valid MIME body header MAY be used (e.g., Content-
   Disposition to indicate the filename), none are specified to have
   special semantics for VPIM and MAY be ignored.  Note that the
   content-type parameter application=faxbw MUST be included in outbound


   Not all VPIM systems support fax, but all SHOULD accept it within the
   multipart/voice-message.  Within a Multipart/Voice-Message, a
   receiving system that cannot render fax content SHOULD accept the
   voice content of a VPIM message and discard the fax content.  Outside
   a Multipart/Voice-Message, a recipient system MAY reject (with
   appropriate NDN) the entire message if it cannot store or is not
   capable of rendering a message with fax attachments.  VPIM conforming
   systems MAY support fax outside of (or without) the Multipart/Voice-
Top   ToC   RFC3801 - Page 23
   Some deployed implementations based on a common interpretation of the
   original VPIM V2 specification reject messages with fax content
   within the Multipart/Voice-Message rather than discard the
   unsupported contents. These systems will return the message to the
   sender with an NDN indicating lack of support for fax.

4.5.  Other MIME Contents

   The following MIME contents (with the exception of multipart/mixed in
   section 4.5.1) MAY be included within a multipart/voice message.
   Other contents MUST NOT be included.  Their handling is a local
   implementation issue.  Multipart/mixed is included to promote
   interoperability with a wider range of systems and also to allow the
   creation of more complex multimedia messages (with a VPIM message as
   one part).

4.5.1.  Multipart/Mixed

   This common MIME content-type allows the enclosing of several body
   parts in a single message.


   A VPIM voice message (i.e., multipart/voice-message) MAY be included
   within a message with a Multipart/Mixed top-level content type.
   Typically, this would only be used when mixing non-voice and non-fax
   contents with a voice message.


   Such a message is not itself a VPIM message and the handling of such
   a construct is outside the scope of the VPIM profile.  However, an
   the spirit of liberal acceptance, a conforming implementation MUST
   accept and render a VPIM voice message contained in a

4.5.2.  Text/Directory


   This content was profiled in the original specification of VPIM v2 as
   a means of transporting contact information from the sender to the
   recipient.  This usage did not find widespread adoption and is no
   longer a feature of VPIM V2.  Conforming implementations SHOULD NOT
   send the Text/Directory content type.
Top   ToC   RFC3801 - Page 24

   For compatibility with an earlier specification of VPIM v2, the
   Text/Directory content type MUST be accepted by a conforming
   implementation, but need not be stored, processed, or rendered to the

4.5.3.  Proprietary Voice or Fax Formats

   Use of any other encoding except the required codecs reduces
   interoperability in the absence of explicit knowledge about the
   capabilities of the recipient.  A conforming implementation SHOULD
   NOT use any other encoding unless a unique identifier is registered
   with the IANA prior to use (see [MIME4]).  The voice encodings SHOULD
   be registered as subtypes of Audio. The fax encodings SHOULD be
   registered as subtypes of Image.


   Proprietary voice encoding formats or other standard formats SHOULD
   NOT be sent under this profile unless the sender has a reasonable
   expectation that the recipient will accept the encoding.  In
   practice, this requires explicit per-destination configuration
   information maintained either in a directory, personal address book,
   or gateway configuration tables.


   Systems MAY accept other Audio/* or Image/* content types if they can
   decode them.  Systems which receive Audio/* or Image/* content types
   which they are unable to deposit or unable to render MUST return the
   message (and SHOULD include the original content) to the originator
   with an NDN indicating media not supported.

4.5.4.  Text/Plain

   MIME requires support of the basic Text/Plain content type (with the
   US-ASCII character set).  This content type has limited applicability
   within the voice-messaging environment.  However, because VPIM is a
   MIME profile, MIME requirements SHOULD be met.


   Conforming VPIM implementations SHOULD NOT send the Text/Plain
   content-type.  Implementations MAY send the Text/Plain content-type
   outside the Multipart/Voice-Message.
Top   ToC   RFC3801 - Page 25

   Within a Multipart/Voice-Message, the Text/Plain content-type MAY be
   dropped from the message, if necessary, to deliver the audio/fax
   components.  The recipient SHOULD NOT reject the entire message if
   the text component cannot be accepted or rendered.

   Outside a Multipart/Voice-Message, conforming implementations MUST
   accept Text/Plain; however, specific handling is left as an
   implementation decision.  From: [MIME2]

   Some deployed implementations based on a common interpretation of the
   original VPIM V2 specification reject messages with any text content
   rather than discard the unsupported contents.  These systems will
   return the message to the sender with an NDN indicating lack of
   support for text.

4.6.  Delivery Status Notification (DSN)

   A DSN is a notification of delivery (positive DSN), non-delivery
   (negative DSN), or temporary delivery delay (delayed DSN).  The top-
   level content-type of a DSN is Multipart/Report, which is defined in
   [REPORT].  The content-type which distinguishes DSN's from other
   types of notifications is Message/Delivery-Status, which is defined
   in [DSN].


   A VPIM-compliant implementation MUST be able to send DSN's that
   conform to [REPORT] and [DSN].  Unless requested otherwise, a non-
   delivery DSN MUST be sent when any form of non-delivery of a message

   A VPIM-compliant implementation SHOULD provide a spoken delivery
   status in the "human-readable" body part of the DSN, but MAY provide
   a textual status.


   A VPIM-compliant implementation MUST be able to receive DSN's that
   conform to [REPORT] and [DSN].

   A VPIM-compliant implementation MUST be able to receive a DSN whose
   "human-readable" body part contains a spoken delivery status phrase
   or a textual description.  Though subsequent use of the phrase or
   text is a local implementation issue, the intent of the DSN MUST be
   presented to the end user.
Top   ToC   RFC3801 - Page 26
4.7.  Message Disposition Notification (MDN)

   An MDN is a notification indicating what happens to a message after
   it is deposited in the recipient's mailbox.  An MDN can be positive
   (message was read/played/rendered/etc.) or negative (message was
   deleted before recipient could see it, etc.).  The top-level
   content-type of a MDN is Multipart/Report, which is defined in
   [REPORT].  The content-type which distinguishes MDN's from other
   types of notifications is Message/Disposition-Notification, which is
   defined in [MDN].


   A VPIM-compliant implementation SHOULD support the ability to request
   MDNs.  This is done via the use of the "Disposition-Notification-To:"
   header field as defined in [MDN].

   A VPIM-compliant implementation SHOULD support the ability to send
   MDNs, but these MDNs MUST conform to [REPORT] and [MDN].

   When sending an MDN, a VPIM-compliant implementation SHOULD provide a
   spoken message disposition in the "human-readable" body part of the
   MDN, but MAY provide a textual status.


   A VPIM-compliant implementation SHOULD respond to an MDN request with
   an MDN response.

   A VPIM-compliant implementation MUST be able to receive MDNs that
   conform to [REPORT] and [MDN], if it is capable of requesting MDNs.
   If a VPIM-compliant implementation is capable of receiving MDNs, it
   MUST be able to receive a MDN whose "human-readable" body part
   contains a spoken message disposition phrase or a textual disposition
   description.  Though subsequent use of the phrase or text is a local
   implementation issue, the intent of the MDN MUST be presented to the
   end user.

4.8.  Forwarded Messages

   VPIM v2 explicitly supports the forwarding of voice and fax content
   with voice or fax annotation.  However, only the two constructs
   described below are acceptable in a VPIM message.  Since only the
   first (i.e., Message/RFC822) can be recognized as a forwarded message
   (or even multiple forwarded messages), it is RECOMMENDED that this
   construct be used whenever possible.
Top   ToC   RFC3801 - Page 27
   Forwarded VPIM messages SHOULD be sent as a Multipart/Voice-Message
   with the entire original message enclosed in a Message/RFC822
   content-type and the annotation as a separate Audio/* or Image/* body
   part.  If the RFC822 header fields are not available for the
   forwarded content, simulated header fields with available information
   SHOULD be constructed to indicate the original sending timestamp, and
   the original sender as indicated in the "From:" field.  Note that at
   least one of "From:", "Subject:", or "Date:" MUST be present.  As
   well, the Message/RFC822 content MUST include at least the "MIME-
   Version:", and "Content-Type:" header fields.  From: [MIME2]

   In the event that forwarding information is lost, the entire audio
   content MAY be sent as a single Audio/* segment without including any
   forwarding semantics.  An example of this loss is an AMIS message
   being forwarded through an AMIS-to-VPIM gateway.

4.9.  Reply Messages

   VPIM v2 explicitly supports replying to received messages.

   Support of multiple originator header fields in a reply message is
   often not possible on voice messaging systems, so it may be necessary
   to choose only one when gatewaying a VPIM message to another voice
   message system.  However, implementers should note that this may make
   it impossible to send DSN's, MDN's, and replies to their proper

   In some cases, replying to a message is not possible, such as with a
   message created by telephone answering (i.e., classic voice mail).
   In this case, the From field SHOULD contain the special address non-
   mail-user@domain (see 4.1.2).  The recipient's VPIM system SHOULD NOT
   offer the option to reply to this kind of message (unless an
   outcalling feature is offered - which is out of scope for VPIM).

(page 27 continued on part 2)

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