Internet Engineering Task Force (IETF)                   R. Ouazana, Ed.
Request for Comments: 9007                                      Linagora
Category: Standards Track                                     March 2021
ISSN: 2070-1721


Handling Message Disposition Notification with the JSON Meta Application
                            Protocol (JMAP)

Abstract

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9007.

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   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction
     1.1.  Notational Conventions
     1.2.  Terminology
     1.3.  Addition to the Capabilities Object
   2.  MDN
     2.1.  MDN/send
     2.2.  MDN/parse
   3.  Samples
     3.1.  Sending an MDN for a Received Email Message
     3.2.  Asking for an MDN When Sending an Email Message
     3.3.  Parsing a Received MDN
   4.  IANA Considerations
     4.1.  JMAP Capability Registration for "mdn"
     4.2.  JMAP Error Codes Registration for "mdnAlreadySent"
   5.  Security Considerations
   6.  Normative References

   Author's Address

1.  Introduction

   JMAP ("The JSON Meta Application Protocol (JMAP)" [RFC8620]) is a
   generic protocol for synchronising data, such as mail, calendars, or
   contacts, between a client and a server.  It is optimised for mobile
   and web environments, and it provides a consistent interface to
   different data types.

   JMAP for Mail ("The JSON Meta Application Protocol (JMAP) for Mail"
   [RFC8621]) specifies a data model for synchronising email data with a
   server using JMAP.  Clients can use this to efficiently search,
   access, organise, and send messages.

   Message Disposition Notifications (MDNs) are defined in [RFC8098] and
   are used as "read receipts", "acknowledgements", or "receipt
   notifications".

   A client can come across MDNs in different ways:

   1.  When receiving an email message, an MDN can be sent to the
       sender.  This specification defines an "MDN/send" method to cover
       this case.

   2.  When sending an email message, an MDN can be requested.  This
       must be done with the help of a header field, as already
       specified by [RFC8098]; the header field can already be handled
       by guidance in [RFC8621].

   3.  When receiving an MDN, the MDN could be related to an existing
       sent message.  This is already covered by [RFC8621] in the
       EmailSubmission object.  A client might want to display detailed
       information about a received MDN.  This specification defines an
       "MDN/parse" method to cover this case.

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   Type signatures, examples, and property descriptions in this document
   follow the conventions established in Section 1.1 of [RFC8620].  Data
   types defined in the core specification are also used in this
   document.

   Servers MUST support all properties specified for the new data types
   defined in this document.

1.2.  Terminology

   The same terminology is used in this document as in the core JMAP
   specification.

   Because keywords are case insensitive in IMAP but case sensitive in
   JMAP, the "$mdnsent" keyword MUST always be used in lowercase.

1.3.  Addition to the Capabilities Object

   Capabilities are announced as part of the standard JMAP Session
   resource; see [RFC8620], Section 2.  This defines a new capability,
   "urn:ietf:params:jmap:mdn".

   The capability "urn:ietf:params:jmap:mdn" being present in the
   "accountCapabilities" property of an account represents support for
   the "MDN" data type, parsing MDNs via the "MDN/parse" method, and
   creating and sending MDN messages via the "MDN/send" method.  Servers
   that include the capability in one or more "accountCapabilities"
   properties MUST also include the property in the "capabilities"
   property.

   The value of this "urn:ietf:params:jmap:mdn" property is an empty
   object both in the account's "accountCapabilities" property and in
   the "capabilities" property.

2.  MDN

   An *MDN* object has the following properties:

   *  forEmailId: "Id|null"

      The Email id of the received message to which this MDN is related.
      This property MUST NOT be null for "MDN/send" but MAY be null in
      the response from the "MDN/parse" method.

   *  subject: "String|null"

      The subject used as "Subject" header field for this MDN.

   *  textBody: "String|null"

      The human-readable part of the MDN, as plain text.

   *  includeOriginalMessage: "Boolean" (default: false)

      If "true", the content of the original message will appear in the
      third component of the multipart/report generated for the MDN.
      See [RFC8098] for details and security considerations.

   *  reportingUA: "String|null"

      The name of the Mail User Agent (MUA) creating this MDN.  It is
      used to build the MDN report part of the MDN.  Note that a "null"
      value may have better privacy properties.

   *  disposition: "Disposition"

      The object containing the diverse MDN disposition options.

   *  mdnGateway: "String|null" (server-set)

      The name of the gateway or Message Transfer Agent (MTA) that
      translated a foreign (non-Internet) message disposition
      notification into this MDN.

   *  originalRecipient: "String|null" (server-set)

      The original recipient address as specified by the sender of the
      message for which the MDN is being issued.

   *  finalRecipient: "String|null"

      The recipient for which the MDN is being issued.  If set, it
      overrides the value that would be calculated by the server from
      the Identity defined in the "MDN/send" method, unless explicitly
      set by the client.

   *  originalMessageId: "String|null" (server-set)

      The "Message-ID" header field [RFC5322] (not the JMAP id) of the
      message for which the MDN is being issued.

   *  error: "String[]|null" (server-set)

      Additional information in the form of text messages when the
      "error" disposition modifier appears.

   *  extensionFields: "String[String]|null"

      The object where keys are extension-field names, and values are
      extension-field values (see [RFC8098], Section 3.3).

   A *Disposition* object has the following properties:

   *  actionMode: "String"

      This MUST be one of the following strings: "manual-action" /
      "automatic-action"

   *  sendingMode: "String"

      This MUST be one of the following strings: "mdn-sent-manually" /
      "mdn-sent-automatically"

   *  type: "String"

      This MUST be one of the following strings: "deleted" /
      "dispatched" / "displayed" / "processed"

   See [RFC8098] for the exact meaning of these different fields.  These
   fields are defined as case insensitive in [RFC8098] but are case
   sensitive in this RFC and MUST be converted to lowercase by "MDN/
   parse".

2.1.  MDN/send

   The "MDN/send" method sends a message in the style of [RFC5322] from
   an MDN object.  When calling this method, the "using" property of the
   Request object MUST contain the capabilities
   "urn:ietf:params:jmap:mdn" and "urn:ietf:params:jmap:mail"; the
   latter because of the implicit call to "Email/set" and the use of
   Identity objects, which is described below.  The method takes the
   following arguments:

   *  accountId: "Id"

      The id of the account to use.

   *  identityId: "Id"

      The id of the Identity to associate with these MDNs.  The server
      will use this identity to define the sender of the MDNs and to set
      the "finalRecipient" field.

   *  send: "Id[MDN]"

      A map of the creation id (client specified) to MDN objects.

   *  onSuccessUpdateEmail: "Id[PatchObject]|null"

      A map of the id to an object containing properties to update on
      the Email object referenced by the "MDN/send" if the sending
      succeeds.  This will always be a backward reference to the
      creation id (see the example below in Section 3.1).

   The response has the following arguments:

   *  accountId: "Id"

      The id of the account used for the call.

   *  sent: "Id[MDN]|null"

      A map of the creation id to an MDN containing any properties that
      were not set by the client.  This includes any properties that
      were omitted by the client and thus set to a default by the
      server.  This argument is null if no MDN objects were successfully
      sent.

   *  notSent: "Id[SetError]|null"

      A map of the creation id to a SetError object for each record that
      failed to be sent or null if all successful.

   In this context, the existing SetError types defined in [RFC8620] and
   [RFC8621] are interpreted as follows:

   notFound:  The reference "forEmailId" cannot be found or has no valid
      "Disposition-Notification-To" header field.

   forbidden:  "MDN/send" would violate an Access Control List (ACL) or
      other permissions policy.

   forbiddenFrom:  The user is not allowed to use the given
      "finalRecipient" property.

   overQuota:  "MDN/send" would exceed a server-defined limit on the
      number or total size of sent MDNs.  It could include limitations
      on sent messages.

   tooLarge:  "MDN/send" would result in an MDN that exceeds a server-
      defined limit for the maximum size of an MDN or more generally, on
      email message.

   rateLimit:  Too many MDNs or email messages have been created
      recently, and a server-defined rate limit has been reached.  It
      may work if tried again later.

   invalidProperties:  The record given is invalid in some way.

   The following is a new SetError:

   mdnAlreadySent:  The message has the "$mdnsent" keyword already set.

   If the "accountId" or "identityId" given cannot be found, the method
   call is rejected with an "invalidArguments" error.

   The client MUST NOT issue an "MDN/send" request if the message has
   the "$mdnsent" keyword set.

   When sending the MDN, the server is in charge of generating the
   "originalRecipient" and "originalMessageId" fields according to
   [RFC8098]. "finalRecipient" will also generally be generated by the
   server based on the provided identity, but if specified by the client
   and allowed (see Section 5), the server will use the client-provided
   value.

   The client is expected to explicitly update each "Email" for which an
   "MDN/send" has been invoked in order to set the "$mdnsent" keyword on
   these messages.  To ensure that, the server MUST reject an "MDN/send"
   that does not result in setting the keyword "$mdnsent".  Thus, the
   server MUST check that the "onSuccessUpdateEmail" property of the
   method is correctly set to update this keyword.

2.2.  MDN/parse

   This method allows a client to parse blobs as messages in the style
   of [RFC5322] to get MDN objects.  This can be used to parse and get
   detailed information about blobs referenced in the "mdnBlobIds" of
   the EmailSubmission object or any email message the client could
   expect to be an MDN.

   The "forEmailId" property can be null or missing if the
   "originalMessageId" property is missing or does not refer to an
   existing message or if the server cannot efficiently calculate the
   related message (for example, if several messages get the same
   "Message-ID" header field).

   The "MDN/parse" method takes the following arguments:

   *  accountId: "Id"

      The id of the account to use.

   *  blobIds: "Id[]"

      The ids of the blobs to parse.

   The response has the following arguments:

   *  accountId: "Id"

      The id of the account used for the call.

   *  parsed: "Id[MDN]|null"

      A map of the blob id to a parsed MDN representation for each
      successfully parsed blob or null if none.

   *  notParsable: "Id[]|null"

      A list of ids given that corresponds to blobs that could not be
      parsed as MDNs or null if none.

   *  notFound: "Id[]|null"

      A list of blob ids given that could not be found or null if none.

   The following additional errors may be returned instead of the "MDN/
   parse" response:

   requestTooLarge:  The number of ids requested by the client exceeds
      the maximum number the server is willing to process in a single
      method call.

   invalidArguments:  If the given "accountId" cannot be found, the MDN
      parsing is rejected with an "invalidArguments" error.

3.  Samples

3.1.  Sending an MDN for a Received Email Message

   A client can use the following request to send an MDN back to the
   sender:

      [[ "MDN/send", {
        "accountId": "ue150411c",
        "identityId": "I64588216",
        "send": {
          "k1546": {
            "forEmailId": "Md45b47b4877521042cec0938",
            "subject": "Read receipt for: World domination",
            "textBody": "This receipt shows that the email has been
                displayed on your recipient's computer.  There is no
                guarantee it has been read or understood.",
            "reportingUA": "joes-pc.cs.example.com; Foomail 97.1",
            "disposition": {
              "actionMode": "manual-action",
              "sendingMode": "mdn-sent-manually",
              "type": "displayed"
            },
            "extension": {
              "EXTENSION-EXAMPLE": "example.com"
            }
          }
        },
        "onSuccessUpdateEmail": {
          "#k1546": {
            "keywords/$mdnsent": true
          }
        }
      }, "0" ]]

   If the email id matches an existing email message without the
   "$mdnsent" keyword, the server can answer:

       [[ "MDN/send", {
         "accountId": "ue150411c",
         "sent": {
           "k1546": {
             "finalRecipient": "rfc822; john@example.com",
             "originalMessageId": "<199509192301.23456@example.org>"
           }
         }
       }, "0" ],
       [ "Email/set", {
         "accountId": "ue150411c",
         "oldState": "23",
         "newState": "42",
         "updated": {
           "Md45b47b4877521042cec0938": {}
         }
       }, "0" ]]

   If the "$mdnsent" keyword has already been set, the server can answer
   an error:

        [[ "MDN/send", {
          "accountId": "ue150411c",
          "notSent": {
            "k1546": {
              "type": "mdnAlreadySent",
              "description" : "$mdnsent keyword is already present"
            }
          }
        }, "0" ]]

3.2.  Asking for an MDN When Sending an Email Message

   This is done with the "Email/set" "create" method of [RFC8621].

   [[ "Email/set", {
     "accountId": "ue150411c",
     "create": {
       "k2657": {
         "mailboxIds": {
           "2ea1ca41b38e": true
         },
         "keywords": {
           "$seen": true,
           "$draft": true
         },
         "from": [{
           "name": "Joe Bloggs",
           "email": "joe@example.com"
         }],
         "to": [{
           "name": "John",
           "email": "john@example.com"
         }],
         "header:Disposition-Notification-To:asText": "joe@example.com",
         "subject": "World domination",
         ...
       }
     }
   }, "0" ]]

   Note the specified "Disposition-Notification-To" header field
   indicating where to send the MDN (usually the sender of the message).

3.3.  Parsing a Received MDN

   The client issues a parse request:

          [[ "MDN/parse", {
            "accountId": "ue150411c",
            "blobIds": [ "0f9f65ab-dc7b-4146-850f-6e4881093965" ]
          }, "0" ]]

   The server responds:

      [[ "MDN/parse", {
        "accountId": "ue150411c",
        "parsed": {
          "0f9f65ab-dc7b-4146-850f-6e4881093965": {
            "forEmailId": "Md45b47b4877521042cec0938",
            "subject": "Read receipt for: World domination",
            "textBody": "This receipt shows that the email has been
                displayed on your recipient's computer.  There is no
                guarantee it has been read or understood.",
            "reportingUA": "joes-pc.cs.example.com; Foomail 97.1",
            "disposition": {
              "actionMode": "manual-action",
              "sendingMode": "mdn-sent-manually",
              "type": "displayed"
            },
            "finalRecipient": "rfc822; john@example.com",
            "originalMessageId": "<199509192301.23456@example.org>"
          }
        }
      }, "0" ]]

   In the case that a blob id is not found, the server would respond:

         [[ "MDN/parse", {
           "accountId": "ue150411c",
           "notFound": [ "0f9f65ab-dc7b-4146-850f-6e4881093965" ]
         }, "0" ]]

   If the blob id has been found but is not parsable, the server would
   respond:

        [[ "MDN/parse", {
          "accountId": "ue150411c",
          "notParsable": [ "0f9f65ab-dc7b-4146-850f-6e4881093965" ]
        }, "0" ]]

4.  IANA Considerations

4.1.  JMAP Capability Registration for "mdn"

   This section registers the "mdn" JMAP Capability in the "JMAP
   Capabilities" registry as follows:

   Capability Name:  "urn:ietf:params:jmap:mdn"
   Intended Use:  common
   Change Controller:  IETF
   Security and Privacy Considerations:  This document, Section 5.
   Reference:  This document

4.2.  JMAP Error Codes Registration for "mdnAlreadySent"

   IANA has registered one new error code in the "JMAP Error Codes"
   registry, as defined in [RFC8620].

   JMAP Error Code:  mdnAlreadySent
   Intended Use:  common
   Change Controller:  IETF
   Description:  The message has the "$mdnsent" keyword already set.
      The client MUST NOT try again to send an MDN for this message.
   Reference:  This document, Section 2.1

5.  Security Considerations

   The same considerations regarding MDN (see [RFC8098] and [RFC3503])
   apply to this document.

   In order to reinforce trust regarding the relation between the user
   sending an email message and the identity of this user, the server
   SHOULD validate in conformance to the provided Identity that the user
   is permitted to use the "finalRecipient" value and return a
   "forbiddenFrom" error if not.

6.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3503]  Melnikov, A., "Message Disposition Notification (MDN)
              profile for Internet Message Access Protocol (IMAP)",
              RFC 3503, DOI 10.17487/RFC3503, March 2003,
              <https://www.rfc-editor.org/info/rfc3503>.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              DOI 10.17487/RFC5322, October 2008,
              <https://www.rfc-editor.org/info/rfc5322>.

   [RFC8098]  Hansen, T., Ed. and A. Melnikov, Ed., "Message Disposition
              Notification", STD 85, RFC 8098, DOI 10.17487/RFC8098,
              February 2017, <https://www.rfc-editor.org/info/rfc8098>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8620]  Jenkins, N. and C. Newman, "The JSON Meta Application
              Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620, July
              2019, <https://www.rfc-editor.org/info/rfc8620>.

   [RFC8621]  Jenkins, N. and C. Newman, "The JSON Meta Application
              Protocol (JMAP) for Mail", RFC 8621, DOI 10.17487/RFC8621,
              August 2019, <https://www.rfc-editor.org/info/rfc8621>.

Author's Address

   Raphaël Ouazana (editor)
   Linagora
   100 Terrasse Boieldieu - Tour Franklin
   92042 Paris - La Défense CEDEX
   France

   Email: rouazana@linagora.com
   URI:   https://www.linagora.com