Adding a Wrong Recipient URL for Handling Misdirected Emails

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Table of Contents

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].¶

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.¶

6. Implementation

7. Additional Requirements

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

8. Examples

List-Unsubscribe: <https://example.com/wrongrecip/uid12345/siga29c83d>
List-Unsubscribe-Post: Wrong-Recipient=One-Click

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 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.¶

10. IANA Considerations

This document makes no requests to IANA.¶

11. 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>.

[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 John Levine for helping shepherd this document as well as 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