Adding a Wrong Recipient URL for Handling Misdirected Emails
draft-ietf-mailmaint-wrong-recipient-05

MAILMAINT                                                      D. Weekly
Internet-Draft                                                          
Updates: 8058 (if approved)                                    J. Levine
Intended status: Standards Track                        30 November 2025
Expires: 3 June 2026

      Adding a Wrong Recipient URL for Handling Misdirected Emails
                draft-ietf-mailmaint-wrong-recipient-05

Abstract

   This document describes a mechanism for an email recipient to
   indicate to a sender that they are not the intended recipient.

About This Document

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

   Discussion of this document takes place on the MAILMAINT Working
   Group mailing list (mailto:mailmaint@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/mailmaint/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/mailmaint/.

   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.

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   This Internet-Draft will expire on 3 June 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Proposal  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   4.  High-Level Goals  . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Out of Scope  . . . . . . . . . . . . . . . . . . . . . . . .   3
   6.  Implementation  . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Mail Senders When Sending . . . . . . . . . . . . . . . .   4
     6.2.  Mail Recipients . . . . . . . . . . . . . . . . . . . . .   4
     6.3.  Mail Senders After Wrong Sender Notification  . . . . . .   4
     6.4.  Header syntax . . . . . . . . . . . . . . . . . . . . . .   4
   7.  Additional Requirements . . . . . . . . . . . . . . . . . . .   5
   8.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Signed HTTPS URI  . . . . . . . . . . . . . . . . . . . .   5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Many users with common names and/or short email addresses receive
   transactional emails from service providers intended for others.
   These emails can't be unsubscribed (as they are transactional) but
   neither are they spam.  These emails commonly are from a noreply@
   email address; there is no standards-based mechanism to report a
   "wrong recipient" to the sender.  Doing so is in the interest of all
   three involved parties: the inadvertent recipient (who does not want
   the email), the sender (who wants to be able to reach their customer
   and who does not want the liability of transmitting PII to a third
   party), and the intended recipient.

   This document proposes a structured mechanism for the reporting of
   such misdirected email via HTTPS POST, updating the List-Unsubscribe-
   Post mechanism of [RFC8058].

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2.  Proposal

   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
   field is present in an email message, the user can select an option
   to indicate that they are not the intended recipient.

   Updating the 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 field 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
   has previously verified the user's email address for the account.

3.  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.

4.  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.

5.  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.

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6.  Implementation

6.1.  Mail Senders When Sending

   Mail Senders that wish to be notified when a misdelivery has occurred
   should include a List-Unsubscribe: header field [RFC2369] and a List-
   Unsubscribe-Post: header containing "Wrong-Recipient=One-Click".

   The sender MUST encode a mapping to the underlying account identifier
   in the List-Unsubscribe: URI as described in Section 3.1 of
   [RFC8058].

6.2.  Mail Recipients

   When a mail client receives an email that includes List-Unsubscribe:
   and List-Unsubscribe-Post: containing "Wrong-Recipient=One-Click"
   header fields, 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 email is reasonably assured to not be spam.

   If the user selects this option, the mail client performs an HTTPS
   POST to the first https URI in the List-Unsubscribe header field as
   described in section 3.2 of [RFC8058].

   The POST body MUST include only "Wrong-Recipient=One-Click".

6.3.  Mail Senders After Wrong Sender Notification

   When a misdelivery has been indicated by a POST to the HTTPS URI or
   email to the given mailto: URI, the sender must make a reasonable
   effort to cease emails to the indicated email address for that user
   account.  Since it is possible that the same address is associated
   with a different valid account, the sender should not simply block
   all mail to that address.

   The sender should make a best effort to attempt to discern a correct
   email address for the user account, such as by using a different
   known email address for that user, postal mail, text message, phone
   call, app push, or presenting a notification in the user interface of
   the service.  How the sender should accomplish this task is not part
   of this specification.

6.4.  Header syntax

   The ABNF grammar in Section 5 of [RFC8058] is augmented as follows:

   postarg =/ "Wrong-Recipient=One-Click"

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7.  Additional Requirements

   The email needs at least one valid authentication identifier, as
   described in Section 4 of [RFC8058].

8.  Examples

8.1.  Signed HTTPS URI

   Header fields in Email:

   List-Unsubscribe: <https://example.com/wrongrecip/uid1234/sig29c83d>
   List-Unsubscribe-Post: Wrong-Recipient=One-Click

   Resulting POST request:

   POST /wrongrecip/uid12345/siga29c83 HTTP/1.1
   Host: example.com
   Content-Length: 25

   Wrong-Recipient=One-Click

9.  Security Considerations

   The considerations are similar to those in Section 6 of [RFC8058].

   A malicious 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.

   A malicious actor might probe to guess where a recipient has an
   account, for example by sending multiple messages pretending to be
   from different banks, and seeing if the recipient marks all but one
   of them "wrong recipient".

   Note that the "wrong recipient" signal does not necessarily mean that
   the address belongs to a real person.  It could have belonged to a
   user who has died, or be a trap that has never belonged to a person
   and mechanically triggers unubscribe or wrong recipient links.

10.  IANA Considerations

   This document makes no requests to IANA.

11.  Normative References

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   [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>.

   [RFC2369]  Neufeld, G. and J. Baer, "The Use of URLs as Meta-Syntax
              for Core Mail List Commands and their Transport through
              Message Header Fields", RFC 2369, DOI 10.17487/RFC2369,
              July 1998, <https://www.rfc-editor.org/rfc/rfc2369>.

   [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>.

   [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>.

Acknowledgments

   Many thanks to Oliver Deighton and Murray Kucherawy for their kind
   and actionable feedback on the language and first draft of the
   proposal.  Thanks to Eliot Lear for helping guide the draft to the
   right hands for review.  A detailed review by Jim Fenton was much
   appreciated and caught a number of key issues.  Many thanks to the
   members of IETF ART for vigorous discussion thereof and for feedback
   from the MAILMAINT working group.

Authors' Addresses

   David Weekly
   Redwood City, CA
   United States of America
   Email: david@weekly.org

   John Levine
   United States of America
   Email: standards@standcore.com

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