| Internet-Draft | Wrong Recipient | December 2023 |
| Weekly | Expires 3 July 2024 | [Page] |
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.¶
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.¶
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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.¶
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.¶
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.¶
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.¶
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.¶
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.¶
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.¶
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¶
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.¶
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.¶
Header in Email¶
Wrong-Recipient: <https://example.com/wrong-recipient?uid=12345&email=user@example.org>
¶
Resulting POST request¶
POST /wrong-recipient?uid=12345&email=user@example.org HTTP/1.1
Host: example.com
¶
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.¶
This document has no IANA actions.¶
TODO¶