Adding a Wrong Recipient URL for Handling Misdirected Emails
draft-dweekly-wrong-recipient-00

Network Working Group                                          D. Weekly
Internet-Draft                                               Capital One
Intended status: Informational                          31 December 2023
Expires: 3 July 2024

      Adding a Wrong Recipient URL for Handling Misdirected Emails
                    draft-dweekly-wrong-recipient-00

Abstract

   This document describes a mechanism for an email recipient to
   indicate that they are not the intended recipient of an email,
   providing that signal back to the originating mail server.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at
   https://dweekly.github.io/ietf-wrong-recipient/draft-dweekly-wrong-
   recipient.html.  Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-dweekly-wrong-recipient/.

   Source for this draft and an issue tracker can be found at
   https://github.com/dweekly/ietf-wrong-recipient.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 3 July 2024.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  High-Level Goals  . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Out of Scope  . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Implementation  . . . . . . . . . . . . . . . . . . . . . . .   3
     5.1.  Mail Senders When Sending . . . . . . . . . . . . . . . .   3
     5.2.  Mail Recipients . . . . . . . . . . . . . . . . . . . . .   4
     5.3.  Mail Senders After Wrong Sender Notification  . . . . . .   4
   6.  Additional Requirements . . . . . . . . . . . . . . . . . . .   4
   7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   5
     10.2.  Informative References . . . . . . . . . . . . . . . . .   5
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Email recipients today have no clear option as to how to best signal
   to a provider that they are not the correct recipient of an email.
   This is a different issue than either an unsubscription request from
   a mailing list or reporting an email as spam, since the service
   itself may be a valid sender attempting to reach some user for a
   valid purpose, but the sender may have inadvertently recorded the
   wrong email address either due to user error or data entry error.

   There is collective benefit to all parties if a service is able to
   detect when an email address is incorrect for a user; the intended
   recipient, the service, and the inadvertent recipient all prefer
   correct delivery.

   Consequently, there ought be a mechanism whereby a service can
   indicate it has an endpoint to indicate a "wrong recipient" of an
   email.  If this header is present in an email message, the user can
   select an option to indicate that they are not the intended
   recipient.

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   Similar to one-click unsubscription [RFC8058], the mail service can
   perform this action in the background as an HTTPS POST to the
   provided URL without requiring the user's further attention to the
   matter.

   Since it's possible the user may have a separate valid account with
   the sending service, it may be important that the sender be able to
   tie _which_ email was sent to the wrong recipient.  For this reason,
   the sender may also include an opaque blob in the header to specify
   the account ID referenced in the email; this is included in the POST.

   Note that this kind of misdelivery shouldn't be possible if a service
   uses email confirmation, such as sending an email address a
   confirmation link to click on at time of enrollment.

2.  Conventions and Definitions

   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.

3.  High-Level Goals

   Allow a recipient to stop receiving emails intended for someone else.

   Allow a service to discover when they have the wrong email for a
   user.

4.  Out of Scope

   This document does not propose a mechanism for automatically
   discovering whether a given user is the correct recipient of an
   email, though it is possible to use some of the signals in an email,
   such as the intended recipient name, to infer a possible mismatch
   between actual and intended recipients.

5.  Implementation

5.1.  Mail Senders When Sending

   Mail Senders that wish to be notified when a misdelivery has occurred
   SHOULD include a Wrong-Recipient header with an HTTPS URI to which
   the recipient's mail client can POST.  If this header is included,
   the mail sender MUST ensure this endpoint is valid.

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   The sender MUST encode a mapping to the underlying account identifier
   in the URI in order to allow the service to know which of their users
   has an incorrect email.

5.2.  Mail Recipients

   When a mail client receives an email that includes a Wrong-Recipient
   header, an option SHOULD be exposed in the user interface that allows
   a recipient to indicate that the mail was intended for another user.

   If the user selects this option, the mail client MUST perform an
   HTTPS POST to the URI in the Wrong-Recipient header

5.3.  Mail Senders After Wrong Sender Notification

   When a misdelivery has been indicated by a POST to the HTTPS URI, the
   sender MUST make a reasonable effort to cease emails to the indicated
   email address for that user account.

   Any GET request to this URI MUST be ignored, since anti-spam software
   may attempt a GET request to URIs mentioned in mail headers.

   The sender SHOULD make a best effort to attempt to discern a correct
   email address for the user account.  How the sender should accomplish
   this task is not part of this specification.

6.  Additional Requirements

   The email needs at least one valid authentication identifier.  In
   this version of the specification the only supported identifier type
   is DKIM [RFC7489], that provides a domain-level identifier in the
   content of the "d=" tag of a validated DKIM-Signature header field.

   The Wrong-Recipient header needs to be included in the "h=" tag of a
   valid DKIM-Signature header field.

   The domain used in the HTTPS URI MUST align with the domain used in
   the "d=" tag of the valid DKIM-Signature header field in which the
   headers are included in the "h=" tag.

7.  Examples

   Header in Email

   Wrong-Recipient: <https://example.com/wrong-
   recipient?uid=12345&email=user@example.org>

   Resulting POST request

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   POST /wrong-recipient?uid=12345&email=user@example.org HTTP/1.1 Host:
   example.com

8.  Security Considerations

   The Wrong-Recipient header will contain the recipient address, but
   that is already exposed in other header fields like To:.

   The user ID of the recipient with the sending service may be exposed
   by the Wrong-Recipient URI, which may not be desired but a sender may
   use an opaque blob to perform a mapping to a user ID on their end
   without leaking any information to outside parties.

   A bad actor with access to the user's email could maliciously
   indicate the recipient was a Wrong Recipient with any services that
   used this protocol, causing mail delivery and potentially account
   access difficulties for the user.

9.  IANA Considerations

   This document has no IANA actions.

10.  References

10.1.  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/rfc/rfc2119>.

   [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/rfc/rfc8174>.

10.2.  Informative References

   [RFC7489]  Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based
              Message Authentication, Reporting, and Conformance
              (DMARC)", RFC 7489, DOI 10.17487/RFC7489, March 2015,
              <https://www.rfc-editor.org/rfc/rfc7489>.

   [RFC8058]  Levine, J. and T. Herkula, "Signaling One-Click
              Functionality for List Email Headers", RFC 8058,
              DOI 10.17487/RFC8058, January 2017,
              <https://www.rfc-editor.org/rfc/rfc8058>.

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Acknowledgments

   TODO

Author's Address

   David Weekly
   Capital One
   Email: david@weekly.org

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