Differences in the text of RFC2421 and draft-ietf-vpim-vpimv2r2-00.txt


*Legend at bottom of page
Text as in RFC2421 Text as in draft-ietf-vpim-vpimv2r2-00.txt
Keyword Section Text Keyword Section Text
MUST 2.1 5) Error reports must be machine-parsable so that helpful responses  can be voiced to users whose only access mechanism is a telephone. MUST 2.1 5) Error reports must be machine-parsable so that helpful responses  can be voiced to users whose only access mechanism is a telephone.
SHOULD NOT 3 Where possible, server implementations should not restrict the number of recipients in a single message. SHOULD NOT 3 Where possible, server implementations should not restrict the number of recipients in a single message.
RECOMMENDED 4.1.1 However, it is RECOMMENDED that public telephone numbers be noted according to the international numbering plan described in [E.164]. RECOMMENDED 4.1.1 However, it is RECOMMENDED that public telephone numbers be noted according to the international numbering plan described in [E.164].
MUST 4.1.2 By convention, a special mailbox named "postmaster" MUST exist on all systems. MUST 4.1.2 By convention, a special mailbox named "postmaster" MUST exist on all systems.
MUST 4.1.2 If a reply to a message is not possible, such as a telephone answering message, then the special address "non-mail-user" must be used as the originator's address. SHOULD 4.1.2 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.
MUST 4.1.2 For compatibility with the installed base of mail user agents, implementations that generate this special address MUST send a negative delivery status notification (DSN) for reply messages sent to the undeliverable address. MUST 4.1.2 For compatibility with the installed base of mail user agents, implementations that generate this special address MUST send a negative delivery status notification (DSN) for reply messages sent to the undeliverable address.
MAY 4.1.3 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. MAY 4.1.3 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.
MUST 4.1.3 If all recipients cannot be presented (e.g. unknown DL expansion) then the recipient header fields MUST be omitted to indicate that an accurate list of recipients (e.g. for use with a reply-all capability) is not known. SHOULD 4.1.3 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.
MUST 4.2 VPIM systems MUST be able to accept and ignore header fields that are not defined here. MUST 4.2 VPIM systems MUST be able to accept and ignore header fields that are not defined here.
MAY 4.2.1 Text names of corporate or positional mailboxes MAY be provided as a simple string. MAY 4.2.1 Text names of corporate or positional mailboxes MAY be provided as a simple string.
      MUST 4.2.1 The originator's fully qualified domain address (a mailbox address followed by the fully qualified domain name) MUST be present.
      SHOULD 4.2.1 Systems compliant with this profile SHOULD provide the text personal name of the voice message originator in a quoted phrase, if the name is available.
      SHOULD 4.2.1 Voice mail machines may not be able to support separate attributes for the "From:" and "Reply-To:" header fields and the SMTP MAIL FROM, VPIM-conforming systems SHOULD set these values to the same address.
      SHOULD 4.2.1 The "From:" address SHOULD be used for replies (see 4.7).
      SHOULD 4.2.2 Systems SHOULD provide a list of recipients only if all recipients are available.
      SHOULD 4.2.2 Systems such as gateways from protocols which do not indicate the complete list of recipients SHOULD provide a "To:" line.
SHOULD NOT 4.2.1 However, if the From address contains <non-mail-user@domain>, the user SHOULD NOT be offered the option to reply, nor should notifications be sent to this address. SHOULD NOT 4.2.1 However, if the "From:" address contains <non-mail-user@domain>, the user SHOULD NOT be offered the option to reply, nor should notifications be sent to this address.
MAY 4.2.2 If present, the addresses in the To header MAY be used for a reply message to all recipients. MAY 4.2.2 If present, the addresses in the "To:" field MAY be used for a reply message to all recipients.
      MAY 4.2.2 There MAY be one or more "To:" fields in any message.
MAY 4.2.2 Systems compliant to this profile MAY also discard the To addresses of incoming messages because of the inability to store the information. MAY 4.2.2 Systems compliant to this profile MAY discard the addresses in the "To:" fields if they are unable to store the information.
MUST NOT 4.2.2 The To header MUST NOT be included in the message if the sending message transport agent (MTA) cannot resolve all the addresses in it, e.g. if an address is a DL alias for which the expansion is unknown (see 4.1.3).      
MAY 4.2.3 Systems compliant to this profile MAY discard the Cc addresses of incoming messages as necessary.      
      MAY 4.2.3 Conforming implementations MAY send "Cc:" lists if all recipients are known at the time of origination.
MAY 4.2.3 If a list of Cc or to addresses is present, these addresses MAY be used for a reply message to all recipients. MAY 4.2.3 If a list of "Cc:" addresses is present, these addresses MAY be used for a reply message to all recipients.
      MAY 4.2.3 Systems compliant 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.
      MAY 4.2.3 Systems compliant 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.
      MUST 4.2.3 The list of disclosed recipients MUST not include undisclosed recipients (ie., those sent via a blind copy).
      SHOULD 4.2.3 If not, systems SHOULD omit the "Cc:" fields to indicate that the full list of recipients is unknown or otherwise unavailable.
      MUST NOT 4.2.3 The list of disclosed recipients MUST not include undisclosed recipients (ie., those sent via a blind copy).
      MAY 4.2.4 This MAY be supplemented by a time zone name in parentheses, e.g., "-0900 (PDT)".
      MUST 4.2.4 The "Date:" field MUST be present and contains the date, time, and time zone in which the message was sent by the originator.
      MUST 4.2.4 The time zone MUST be present and SHOULD be represented in a four-digit time zone offset, such as -0500 for North American Eastern Standard Time.
      SHOULD 4.2.4 Compliant implementations SHOULD be able to convert [RFC822] date and time stamps into local time.
      SHOULD 4.2.4 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.
MUST 4.2.4 The sending system MUST report the time the message was sent MUST 4.2.4 The sending system MUST report the time the message was sent.
MAY 4.2.5 The Sender header field contains the actual address of the originator if the message is sent by an agent on behalf of the author indicated in the From: field. This header field MAY be sent by VPIM conforming system. MAY 4.2.5 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.
      MAY 4.2.5 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.
MUST 4.2.6 Any error messages resulting from the delivery failure MUST be sent to this address (see [DRPT] for additional details). MUST 4.2.6 Any error messages resulting from the delivery failure MUST be sent to this address.
      MUST 4.2.6 Systems that do not support the return path MUST ensure that at the time the message is acknowledged, the message is delivered to the recipient's ultimate mailbox.
MUST NOT 4.2.6 Note that if the Return-path is null ("<>"), e.g. no path, loop prevention or confidential, a notification MUST NOT be sent. MUST NOT 4.2.6 Note that if the "Return-path:" is null ("<>"), e.g. no path, loop prevention or confidential, delivery status and message disposition notifications MUST NOT be sent.
      MUST NOT 4.2.6 The originator system MUST not add this header. (RETURN-PATH)
      SHOULD NOT 4.2.6 Non-Delivery notifications should not be sent after that final delivery.
      MUST 4.2.6 If the receiving system is incapable of storing the return path to be used for subsequent delivery errors, the receiving system must otherwise ensure that further delivery errors don't happen.
MAY 4.2.7 The message-id is not required to be stored on the receiving system. This identifier MAY be used for tracking, auditing, and returning receipt notification reports. MAY 4.2.7 The message id is not required to be stored on the receiving system. This identifier MAY be used for tracking, auditing, and returning receipt notification reports.
MUST 4.2.7 A unique message-id MUST be generated for each message sent from a compliant implementation. MUST 4.2.7 A unique message-id MUST be generated for each message sent from a VPIM-compliant implementation.
      MUST 4.2.8 If only one address of the originator is supported in the message store or in the next-hop protocol from a multi-protocol gateway, the address in the "From:" field MUST be used and the "Reply-To:" field MAY be silently discarded.
      MAY 4.2.8 If only one address of the originator is supported in the message store or in the next-hop protocol from a multi-protocol gateway, the address in the "From:" field MUST be used and the "Reply-To:" field MAY be silently discarded.
SHOULD NOT 4.2.8 A compliant system SHOULD NOT send a Reply-To header. SHOULD NOT 4.2.8 A compliant system SHOULD NOT send a Reply-To header.
MAY 4.2.8 However, if a reply-to header is present, a reply-to sender message MAY be sent to the address specified (that is, overwriting From). MAY 4.2.8 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).
MUST 4.2.8 This preferred address of the originator must also be provided in the originator's vCard EMAIL attribute, if present (see 4.3.3).      
MAY 4.2.9 These header fields MAY be ignored or deleted when the message is received at the final destination. MAY 4.2.9 These header fields MAY be ignored or deleted when the message is received at the final destination.
      SHOULD 4.2.9 When acting as a gateway, information about the system translated from SHOULD be included.
MUST 4.2.9 A compliant system MUST add Received header fields when acting as a gateway and MUST NOT remove any Received fields when relaying messages to other  MTAs or gateways MUST 4.2.9 A VPIM-compliant system MUST add a "Received:" field. When acting as a gateway, information about the system translated from SHOULD be included.
MUST NOT 4.2.9 A compliant system MUST add Received header fields when acting as a gateway and MUST NOT remove any Received fields when relaying messages to other  MTAs or gateways. SHOULD NOT 4.2.9 A VPIM-compliant system SHOULD NOT remove any "Received:" fields when relaying messages to other MTAs or gateways.
SHOULD 4.2.10 Systems compliant with this specification SHOULD include a comment with the words "(Voice 2.0)". SHOULD 4.2.10 Systems compliant with this specification SHOULD include a comment with the words "(Voice 2.0)".
SHOULD 4.2.10 Instead, the presence of the content defined in [V-MSG] SHOULD be used if identification is necessary. SHOULD 4.2.10 Instead, the presence of the content defined in [V-MSG] SHOULD be used if identification is necessary.
SHOULD NOT 4.2.10 This identifier is intended for information only and SHOULD NOT be used to semantically identify the message as being a VPIM message. SHOULD NOT 4.2.10 This identifier is intended for information only and SHOULD NOT be used to semantically identify the message as being a VPIM message.
SHOULD 4.2.11 The typical top level content in a VPIM Message SHOULD be multipart/voice-message, a mechanism for bundling several components into a single identifiable voice message. SHOULD 4.2.11 The typical top level content in a VPIM Message SHOULD be multipart/voice-message.
MUST 4.2.12 Compliant implementations MUST recognize and decode the standard encodings, "Binary", "7bit, "8bit", "Base64" and "Quoted-Printable". MUST 4.2.12 Compliant implementations MUST recognize and decode the standard encodings, "Binary", "7bit, "8bit", "Base64" and "Quoted-Printable".
MUST 4.2.13 If a sensitivity header is present in the message, a compliant system MUST prohibit the recipient from forwarding this message to any other user. MUST 4.2.13 If a "Sensitivity:" field with a value of "Personal" or "Private" is present in the message, a compliant system MUST prohibit the recipient from forwarding this message to any other user.
MUST 4.2.13 If the receiving system does not support privacy and the sensitivity is one of "Personal" or "Private", a negative delivery status notification must sent to the originator with the appropriate status code indicating that privacy could not be assured. MUST 4.2.13 If the receiving system does not support privacy and the sensitivity is one of "Personal" or "Private", a negative delivery status notification MUST be sent to the originator with the appropriate status code (X.Y.Z) indicating that privacy could not be assured.
      SHOULD 4.2.13 If the message is of "Normal" sensitivity, this field SHOULD be omitted.
SHOULD 4.2.13 A compliant system, however, SHOULD allow the responder to reply to a sensitive message, but SHOULD NOT include the original message content. SHOULD 4.2.13 A compliant system, however, SHOULD allow the responder to reply to a sensitive message, but SHOULD NOT include the original message content.
SHOULD 4.2.13 The message contents SHOULD  be returned to the sender to allow for a voice context with the notification. SHOULD 4.2.13 The message contents SHOULD be returned to the sender to allow for a voice context with the notification.
MAY 4.2.13 The sensitivity of the reply message MAY be set by the responder. MAY 4.2.13 The responder MAY set the sensitivity of the reply message.
SHOULD NOT 4.2.13 A compliant system, however, SHOULD allow the responder to reply to a sensitive message, but SHOULD NOT include the original message content. SHOULD NOT 4.2.13 A compliant system, however, SHOULD allow the responder to reply to a sensitive message, but SHOULD NOT include the original message content.
SHOULD NOT 4.2.13 A non-delivery notification to a private message SHOULD NOT be tagged private since it will be sent to the originator. SHOULD NOT 4.2.13 A non-delivery notification to a private message SHOULD NOT be tagged private since it will be sent to the originator.
MAY 4.2.14 Compliant implementations MAY use this header to indicate the importance of a message and may order messages in a recipient's mailbox. From: [X.400]. MAY 4.2.14 Compliant implementations MAY include this header to indicate the importance of a message
SHOULD 4.2.15 For compatibility with text based mailbox interfaces, a text subject field SHOULD be generated by a compliant implementation but MAY be discarded if present by a receiving system. SHOULD 4.2.15 For compatibility with text based mailbox interfaces, a text subject field SHOULD be generated by a compliant implementation.
MAY 4.2.15 For compatibility with text based mailbox interfaces, a text subject field SHOULD be generated by a compliant implementation but MAY be discarded if present by a receiving system. MAY 4.2.15 The subject MAY be discarded if present by a receiving system.
      RECOMMENDED 4.2.15 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.
MAY 4.2.16 This header MAY be present to indicate that the sender is requesting a receipt notification from the receiving user agent. MAY 4.2.16 This header MAY be present to indicate that the sender is requesting a receipt notification from the receiving user agent.
      MAY 4.2.16 VPIM-compliant implementations MAY include this header to request a disposition indication such as a listen confirmation.
MAY 4.2.17 This header MAY be present to define future extensions parameters for an MDN requested by the presence of the header in the previous section. MAY 4.2.17 This header MAY be present to define future extension parameters for an MDN requested by the presence of the header in the previous section.
MUST 4.2.17 However, this header MUST be parsed if present, if MDNs are supported. MUST 4.2.17 However for forward compatibility with future extensions, this header MUST be processed if present, if MDNs are supported.
MUST NOT 4.2.17 If it contains a extension parameter that is required for proper MDN generation (noted with "=required"), then an MDN MUST NOT be sent if the parameter is not understood. MUST NOT 4.2.17 If it contains a extension parameter that is required for proper MDN generation (noted with "=required"), then an MDN MUST NOT be sent if the parameter is not understood.
      SHOULD NOT 4.2.17 Sending systems SHOULD NOT request disposition notification options by sending a disposition-notification-options header.
MUST 4.3 When binary transport is not available, implementations MUST encode the audio and/or facsimile data as Base64 MUST 4 When binary transport is not available, implementations MUST encode the audio and/or facsimile data as Base64.
SHOULD 4.3 An implementation in compliance with this profile SHOULD send audio and/or facsimile data in binary form when binary message transport is available. SHOULD 4 An implementation in compliance with this profile SHOULD send audio and/or facsimile data in binary form when binary message transport is available (see section 5). 
SHOULD 4.3 The presence of other contents within a VPIM voice message is an error condition and SHOULD result in a negative delivery status notification.      
SHOULD 4.3 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. SHOULD 4.4 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.
MUST 4.3 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. MUST 4 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.
MUST 4.3 However, if a content is received in a transfer encoding that cannot be rendered to the user, an appropriate negative delivery status notification MUST be sent MUST 4 However, if a content is received in a transfer encoding that cannot be rendered to the user, an appropriate negative delivery status notification MUST be sent.
      MAY 4.3.1 This field MAY be present to facilitate the text identification of these body parts in simple email readers.
MUST 4.3.1 The Multipart/Voice-Message content-type MUST only contain the profiled media and content types specified in this section (i.e. audio/*, image/*, message/rfc822 and text/directory) MUST 4.4.1 The Multipart/Voice-Message content-type MUST only contain the profiled media and content types specified in this section (i.e. audio/*, image/*, message/rfc822 and text/directory).
MUST 4.3.1 Conformant implementations MUST send the multipart/voice-message in a VPIM message MUST 4.4.1 Conformant implementations MUST send the multipart/voice-message in a VPIM message.
MUST 4.3.1 Conformant implementations MUST recognize the Multipart/Voice-Message content (whether it is a top level content or below a multipart/mixed) and be able to separate the contents (e.g. spoken name or spoken subject). MUST 4.4.1 Conformant implementations MUST recognize the Multipart/Voice-Message content (whether it is a top-level content or below a multipart/mixed) and be able to separate the contents (e.g. spoken name or spoken subject).
      MUST 4.4.3 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 recipient.
MUST 4.3.3 Each vCard MUST be contained within a Text/Directory content type [MIMEDIR] within a VPIM message.      
MUST 4.3.3 [MIMEDIR] requires that the character set MUST be defined as a parameter value (typically us-ascii for VPIM)      
MUST 4.3.3 (the value MUST be vCard within VPIM messages)      
MUST 4.3.3 Each VPIM message SHOULD be created with a Text/Directory (vCard profile) content type that MUST contain the preferred email address, telephone number, and text name of the message originator as well as the vCard version.      
MUST 4.3.3 If the text/directory content-type is included in a VPIM message, the vCard profile [VCARD] MUST be used and MUST specify at least the following attributes:      
MUST 4.3.3 VERSION - Indicates the version of the vCard profile.  Version 3.0 [VCARD] MUST be used.      
MUST 4.3.3 Because it is expected that recipients using a telephone user interface will use the information in the vCard to identify the originator, and the GUI will see the information presented in the FROM line, all present components in the text name of the FROM header field MUST match the values provided by the Vcard.      
MUST 4.3.3 If present, the spoken name attribute MUST be denoted by a content ID pointing to an audio/* content elsewhere in the VPIM message.      
MUST 4.3.3 A typical VPIM message (i.e. no forwarded parts), MUST only contain one vCard -- more than one is an error condition.      
MUST 4.3.3 However, these vCards MUST be associated with the originator(s) of the forwarded message(s) and the originator of the forwarding message.      
SHOULD 4.3.3 [MIMEDIR] requires that the character set MUST be defined as a parameter value (typically us-ascii for VPIM) and that the profile SHOULD be defined (the value MUST be vCard within VPIM messages).      
SHOULD 4.3.3 Each VPIM message SHOULD be created with a Text/Directory (vCard profile) content type that MUST contain the preferred email address, telephone number, and text name of the message originator as well as the vCard version.      
SHOULD 4.3.3 The vCard SHOULD contain the spoken name and role of the originator, as well as the revision date.       
SHOULD 4.3.3 The following attributes SHOULD be specified:      
MAY 4.3.3 Any other vCard attribute MAY also be present.      
MAY 4.3.3 The vCard MAY use other attributes as defined in [VCARD] or extensions attributes not yet defined (e.g. capabilities).      
MAY 4.3.4 While any valid MIME body header MAY be used, several header fields have the following semantics when included with this body part:      
MUST 4.3.4 An implementation compliant to this profile MUST send Audio/32KADPCM by default for voice [ADPCM]. MUST 4.4.4 An implementation compliant to this profile MUST send Audio/32KADPCM by default for voice [ADPCM].
MUST 4.3.4 Receivers MUST be able to accept and decode Audio/32KADPCM. MUST 4.4.4 Receivers MUST be able to accept and decode Audio/32KADPCM.
MUST 4.3.4 Note that if an Originator Spoken Name audio body and a vCard are both present in a VPIM message, the vCard SOUND attribute MUST point to this audio body (see 4.3.3).      
RECOMMENDED 4.3.4 It is RECOMMENDED that this be done in the same order as they were sent. RECOMMENDED 4.4.4 It is RECOMMENDED that this be done in the same order as they were sent.
SHOULD 4.3.4 If an implementation can only handle one voice body, then multiple voice bodies (if present) SHOULD be concatenated, and SHOULD NOT be discarded. SHOULD 4.4.4 If an implementation can only handle one voice body, then multiple voice bodies (if present) SHOULD be concatenated, and SHOULD NOT be discarded.
SHOULD NOT 4.3.4 If an implementation can only handle one voice body, then multiple voice bodies (if present) SHOULD be concatenated, and SHOULD NOT be discarded. SHOULD 4.4.4 If an implementation can only handle one voice body, then multiple voice bodies (if present) SHOULD be concatenated, and SHOULD NOT be discarded.
MAY 4.3.4.1 This field MAY be present to facilitate the text identification of these body parts in simple email readers.      
MUST 4.3.4.2 This field (Content-Disposition) MUST be present to allow the parsable identification of these body parts. MUST 4.3.2 This field (Content-Disposition) MUST be present to allow the parsable identification of body parts within a VPIM voice message.
MUST 4.3.4.2 Since a VPIM voice message is intended to be automatically played upon display of the message, in the order in which the audio contents occur, the audio contents must always be of type inline. MUST 4.3.2 Since a VPIM voice message is intended to be automatically played upon display of the message, in the order in which the audio contents occur, the audio contents must always be of type inline.
SHOULD 4.3.4.3 Note that there SHOULD only be one instance of each of these types of audio contents per message level. SHOULD 4.3.2 Note that there SHOULD only be one instance of each of these types of audio contents per message level.
MAY 4.3.4.3 This field MAY be present to allow the specification of the length of the audio bodypart in seconds. MAY 4.3.3 This field MAY be present to allow the specification of the length of the audio bodypart in seconds.
MAY 4.3.4.4 This field MAY be present to allow the specification of the spoken language of the audio bodypart. MAY 4.3.4 This field MAY be present to allow the specification of the spoken language of the audio bodypart.
      SHOULD NOT 4.4 Conforming implementations SHOULD NOT create a message containing prohibited contents.
      MAY 4.4 In the spirit of liberal acceptance, a conforming implementation MAY accept and render prohibited content.
      MAY 4.4 unable to accept or render prohibited contents MAY discard the contents as necessary to deliver the voice content.
      SHOULD 4.4.2 This body part SHOULD be used within a multipart/voice-message to forward complete messages (see 4.6) or to reply with original content (see 4.7).
      SHOULD 4.4.2 The receiving system SHOULD treat this attachment as a forwarded message.
      SHOULD NOT 4.4.3 Conforming implementations SHOULD NOT send the text/directory content type.
      SHOULD NOT 4.4.4 If an implementation can only handle one voice body, then multiple voice bodies (if present) SHOULD be concatenated, and SHOULD NOT be discarded.
MUST 4.3.5 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. MUST 4.4.5 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.
MUST 4.3.5 An implementation MAY send this fax content in VPIM voice messages and MUST be able to recognize and display it in received messages.      
MUST 4.3.5 If a fax message is received that cannot be rendered to the user (e.g. the receiving VPIM system does not support fax), then the system MUST return the message with a negative delivery status notification with a media not supported status code.      
MUST 4.3.5 Note that the content type parameter application=faxbw MUST be included in outbound messages. MUST 4.4.5 Note that the content type parameter application=faxbw MUST be included in outbound messages.
MUST 4.3.5 However, inbound messages with or without this parameter MUST be rendered to the user MUST 4.4.5 Inbound messages in the multipart/voice-message with or without the application parameter MUST be rendered to the user.
      MUST 4.4.5 Those that do MUST support it within the multipart/voice-message and MAY support it outside of the multipart/voice-message.
MUST 4.3.5 (if the rendering software encounters an error in the file format, some form of negative delivery status notification MUST be sent to the originator). SHOULD 4.4.5 If the rendering software encounters an error in the file format, some form of negative delivery status notification SHOULD be sent to the originator.
SHOULD 4.3.5 All VPIM implementations that support facsimile SHOULD generate TIFF-F compatible facsimile contents in the image/tiff; application=faxbw sub-type encoding by default. MUST 4.4.5 All VPIM implementations that support facsimile MUST generate TIFF-F compatible facsimile contents in the image/tiff; application=faxbw sub-type encoding by default.
MAY 4.3.5 An implementation MAY send this fax content in VPIM voice messages and MUST be able to recognize and display it in received messages.      
MUST 4.3.5 An implementation MAY send this fax content in VPIM voice messages and MUST be able to recognize and display it in received messages.      
MAY 4.3.5 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. MAY 4.4.5 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.
      MAY 4.4.5 Those that do MUST support it within the multipart/voice-message and MAY support it outside of the multipart/voice-message.
      MAY 4.4.5 Outside a multipart/voice-message, a recipient system MAY reject (with appropriate NDN) the entire message if it cannot handle the fax attachments.
      SHOULD 4.4.5 If the VPIM message is a voice annotated fax, the implementation SHOULD send this fax content in multipart/voice-message.
      SHOULD 4.4.5 Not all VPIM systems support fax, but all SHOULD accept it.
      SHOULD 4.4.5 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.
MAY 4.3.6 Proprietary voice or fax encoding formats or other standard formats MAY be supported under this profile provided a unique identifier is registered with the IANA prior to use (see [MIME4]). MAY 4.4.6 Proprietary voice encoding formats or other standard formats MAY be sent under this profile only if the sender has a reasonable expectation that the recipient will accept the encoding.
MAY 4.3.6 A compliant implementation MAY use any other encoding with explicit per-destination configuration. MAY 4.4.6 A compliant implementation MAY use any other encoding provided a unique identifier is registered with the IANA prior to use (see [MIME4]).
      MAY 4.4.6 Systems MAY accept other audio/* or image/* content types if they can decode them.
      MUST 4.4.6 Systems which receive audio/* or image/* content types which they are unable to decode MUST return the message to the originator with an NDN indicating media not supported.
MUST 4.4 Implementations MUST issue negative delivery status notifications to the originator when any form of non-delivery to the recipient occurs.