Internet DRAFT - draft-benecke-cfbl-address-header
draft-benecke-cfbl-address-header
Network Working Group J. Benecke
Internet-Draft CleverReach GmbH & Co. KG
Intended status: Experimental 7 May 2023
Expires: 8 November 2023
Complaint Feedback Loop Address Header
draft-benecke-cfbl-address-header-13
Abstract
This document describes a method that allows a Message Originator to
specify a complaint feedback loop (FBL) address as a message header
field. Also, it defines the rules for processing and forwarding such
a complaint. The motivation for this arises out of the absence of a
standardized and automated way to provide Mailbox Providers with an
address for a complaint feedback loop. Currently, providing and
maintaining such an address is a manual and time-consuming process
for Message Originators and Mailbox Providers.
The mechanism specified in this document is being published as an
experiment, to gauge interest of, and gather feedback from
implementers and deployers. This document is produced through the
Independent RFC stream and was not subject to the IETF's approval
process.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 8 November 2023.
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
and restrictions with respect to this document.
Table of Contents
1. Introduction and Motivation . . . . . . . . . . . . . . . . . 3
1.1. Scope of this Experiment . . . . . . . . . . . . . . . . 4
1.2. How CFBL differs from One-Click-Unsubscribe . . . . . . . 5
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Received Message . . . . . . . . . . . . . . . . . . . . 5
3.1.1. Strict . . . . . . . . . . . . . . . . . . . . . . . 6
3.1.2. Relaxed . . . . . . . . . . . . . . . . . . . . . . . 6
3.1.3. Third Party Address . . . . . . . . . . . . . . . . . 7
3.1.4. DKIM Signature . . . . . . . . . . . . . . . . . . . 8
3.2. Multiple CFBL-Address Header Fields . . . . . . . . . . . 8
3.3. CFBL-Feedback-ID Header Field . . . . . . . . . . . . . . 8
3.4. Receiving Report Address . . . . . . . . . . . . . . . . 8
3.5. Feedback Message . . . . . . . . . . . . . . . . . . . . 9
3.5.1. XARF Report . . . . . . . . . . . . . . . . . . . . . 9
4. Implementation . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Message Originator . . . . . . . . . . . . . . . . . . . 9
4.2. Mailbox Provider . . . . . . . . . . . . . . . . . . . . 10
5. Header Field Syntax . . . . . . . . . . . . . . . . . . . . . 10
5.1. CFBL-Address . . . . . . . . . . . . . . . . . . . . . . 10
5.2. CFBL-Feedback-ID . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6.1. Attacks on the Feedback Loop Address . . . . . . . . . . 11
6.2. Automatic Suspension of an Account . . . . . . . . . . . 11
6.3. Enumeration Attacks / Provoking Unsubscription . . . . . 11
6.4. Data Privacy . . . . . . . . . . . . . . . . . . . . . . 12
6.5. Abusing for Validity and Existence Queries . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7.1. CFBL-Address . . . . . . . . . . . . . . . . . . . . . . 13
7.2. CFBL-Feedback-ID . . . . . . . . . . . . . . . . . . . . 13
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Simple . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.2. Data Privacy Safe Report . . . . . . . . . . . . . . . . 15
8.3. Data Privacy Safe Report with HMAC . . . . . . . . . . . 15
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction and Motivation
This memo extends the complaint feedback loop recommendations
described in {!RFC6449}} with an automated way to provide the
necessary information by the Message Originator to Mailbox Providers.
The reader should be familiar with the terminology and concepts in
that document; terms beginning with capital letters used in this memo
are described in that document.
As described in [RFC6449], the registration for such a complaint
feedback loop needs to be done manually by a human at any Mailbox
Provider who provides a complaint feedback loop. The key
underpinning of [RFC6449] is that access to the complaint feedback
loop is a privilege, and that Mailbox Providers are not prepared to
send feedback to anyone they cannot reasonably believe are
legitimate. However, manual registration and management can be quite
time-consuming if there are new feedback loops rising up, or if the
Message Originator wants to add new IP addresses, DKIM domains or
change their complaint address. In addition, a manual process is not
well suited and/or feasible for smaller Mailbox Providers.
Here we propose that Message Originators add a header field without
the need to manually register with each Feedback Provider, and that
willing Mailbox Providers can use it to send the Feedback Messages to
the specified complaint address. This simplification or extension of
a manual registration and verification process would be another
advantage for the Mailbox Providers.
A new message header field, rather than a new DNS record, was chosen
to easily distinguish between multiple Message Originators without
requiring user or administrator intervention. For example, if a
company uses multiple systems, each system can set this header field
on its own without requiring users or administrators to make any
changes to their DNS. No additional DNS lookup is required of the
Mailbox Provider side to obtain the complaint address.
The proposed mechanism is capable of being operated in compliance
with the data privacy laws e.g. GDPR or CCPA. As described in
Section 6.4, a Feedback Message may contain personal data, this
document describes a way to omit this personal data when sending the
Feedback Message and only send back a header field.
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Nevertheless, the described mechanism below potentially permits a
kind of man-in-the-middle attack between the domain owner and the
recipient. A bad actor can generate forged reports to be "from" a
domain name the bad actor is attacking and send this reports to the
complaint feedback loop address. These fake messages can result in a
number of actions, such as blocking of accounts or deactivating
recipient addresses. This potential harm and others are described
with potential countermeasures in Section 6.
In summary, this document has the following objectives:
* Allow Message Originators to signal that a complaint address
exists without requiring manual registration with all providers.
* Allow Mailbox Providers to obtain a complaint address without
developing their own manual registration process.
* Be able to provide a complaint address to smaller Mailbox
Providers who do not have a feedback loop in place
* Provide a data privacy safe option for a complaint feedback loop.
1.1. Scope of this Experiment
The CFBL-Address header field and the CFBL-Feedback-ID header field
comprise an experiment. Participation in this experiment consists of
adding the CFBL-Address header field on Message Originators side or
by using the CFBL-Address header field to send Feedback Messages to
the provided address on Mailbox Provider side. Feedback on the
results of this experiment can be emailed to the author, raised as an
issue at https://github.com/jpbede/rfc-cfbl-address-header/ or can be
emailed to the IETF cfbl mailing list (cfbl@ietf.org).
The goal of this experiment is to answer the following questions
based on real-world deployments:
* Is there interest among Message Originator and Mailbox Providers?
* If the Mailbox Provider adds this capability, will it be used by
the Message Originators?
* If the Message Originator adds this capability, will it be used by
the Mailbox Providers?
* Does the presence of the CFBL-Address and CFBL-Feedback-ID header
field introduce additional security issues?
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* What additional security measures/checks need to be performed at
the Mailbox Provider before a Feedback Message is sent?
* What additional security measures/checks need to be performed at
the Message Originator after a Feedback Message is received?
This experiment will be considered successful if the CFBL-Address
header field is used by a leading Mailbox Provider and by at least
two Message Originators within the next two years and these parties
successfully use the address specified in the header field to
exchange Feedback Messages.
If this experiment is successful and these header fields prove to be
valuable and popular, the header fields may be taken to the IETF for
further discussion and revision.
1.2. How CFBL differs from One-Click-Unsubscribe
For good reasons, the One-Click-Unsubscribe [RFC8058] signaling
already exists, which may have several interests in common with this
document. However, this header field requires the List-Unsubscribe
header field, whose purpose is to provide the link to unsubscribe
from a list. For this reason, this header field is only used by
operators of broadcast marketing lists or mailing lists, not in
normal email traffic.
2. 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.
The key word "CFBL" in this document is the abbreviation for
"complaint feedback loop" and will hereafter be used.
Syntax descriptions use ABNF [RFC5234] [RFC7405].
3. Requirements
3.1. Received Message
This section describes the requirements that a received message, the
message that is sent from the Message Originator to the Mailbox
Provider and about which a report is to be sent later, must meet.
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3.1.1. Strict
If the domain in the [RFC5322].From and the domain in the CFBL-
Address header field are identical, this domain MUST be matched by a
valid [DKIM] signature. In this case, the DKIM "d=" parameter and
the [RFC5322].From field have identical domains. This signature MUST
meet the requirements described in Section 3.1.4.
The following example meets this case:
Return-Path: <sender@mailer.example.com>
From: Awesome Newsletter <newsletter@example.com>
To: receiver@example.org
Subject: Super awesome deals for you
CFBL-Address: fbl@example.com; report=arf
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@mailer.example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=example.com; s=news;
h=Subject:From:To:Message-ID:CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
3.1.2. Relaxed
If the domain in CFBL-Address header field is a child domain of the
[RFC5322].From, the [RFC5322].From domain MUST be matched by a valid
[DKIM] signature. In this case, the DKIM "d=" parameter and the
[RFC5322].From domain have a identical (Example 1) or parent (Example
2) domain. This signature MUST meet the requirements described in
Section 3.1.4.
Example 1:
Return-Path: <sender@mailer.example.com>
From: Awesome Newsletter <newsletter@mailer.example.com>
To: receiver@example.org
Subject: Super awesome deals for you
CFBL-Address: fbl@mailer.example.com; report=arf
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@mailer.example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=example.com;
h=Content-Type:Subject:From:To:Message-ID:
CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
Example 2:
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Return-Path: <sender@mailer.example.com>
From: Awesome Newsletter <newsletter@example.com>
To: receiver@example.org
Subject: Super awesome deals for you
CFBL-Address: fbl@mailer.example.com; report=arf
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@mailer.example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=example.com;
h=Content-Type:Subject:From:To:Message-ID:
CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
3.1.3. Third Party Address
If the domain in [RFC5322].From differs from the domain in the CFBL-
Address header field, an additional valid [DKIM] signature MUST be
added that matches the domain in the CFBL-Address header field. The
other existing valid [DKIM] signature MUST match the domain in the
[RFC5322].From header field. This double DKIM signature ensures that
both, the domain owner of the [RFC5322].From domain and the domain
owner of the CFBL-Address domain, agree who should receive the
Feedback Messages. Both signature MUST meet the requirements
described in Section 3.1.4.
The following example meets this case:
Return-Path: <sender@saas-mailer.example>
From: Awesome Newsletter <newsletter@example.com>
To: receiver@example.org
Subject: Super awesome deals for you
CFBL-Address: fbl@saas-mailer.example; report=arf
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=saas-mailer.example; s=system;
h=Subject:From:To:Message-ID:CFBL-Feedback-ID:CFBL-Address;
DKIM-Signature: v=1; a=rsa-sha256; d=example.com; s=news;
h=Subject:From:To:Message-ID:CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
An Email Service Provider may accept pre-signed messages from its
Message Authors, making it impossible for it to apply the double
signature described above, in which case the double signature MUST BE
omitted and the Email Service Provider MUST sign with its domain.
Therefore, the pre-signed message MUST NOT include "CFBL-Address" and
"CFBL-Feedback-ID" in its h= tag.
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This way the Email Service Provider has the possibility to accept the
pre-signed messages and can inject their own CFBL-Address.
The following example meets this case:
Return-Path: <newsletter@example.com>
From: Awesome Newsletter <newsletter@example.com>
To: receiver@example.org
Subject: Super awesome deals for you
CFBL-Address: fbl@saas-mailer.example; report=arf
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=example.com; s=news;
h=Subject:From:To:Message-ID;
DKIM-Signature: v=1; a=rsa-sha256; d=saas-mailer.example; s=system;
h=Subject:From:To:Message-ID:CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
3.1.4. DKIM Signature
When present, CFBL-Address and CFBL-Feedback-ID header fields MUST be
included in the "h=" tag of the aforementioned valid DKIM signature.
If the domain is neither matched by a valid DKIM signature nor the
header field is covered by the "h=" tag, the Mailbox Provider SHALL
NOT send a report message.
3.2. Multiple CFBL-Address Header Fields
A Message can contain multiple CFBL-Address header fields. These
multiple header fields MUST be treated as a list of receive report
addresses so that each address can receive a report.
3.3. CFBL-Feedback-ID Header Field
The Message Originator MAY include a CFBL-Feedback-ID header field in
its messages out of various reasons, e.g. their feedback loop
processing system can't do anything with the Message-ID header field.
It is RECOMMENDED that the header field include a hard to forge
protection component such as an [HMAC] using a secret key, instead of
a plain-text string.
3.4. Receiving Report Address
The receiving report address provided in the CFBL-Address header
field MUST accept [ARF] reports.
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The Message Originator can OPTIONALLY request a [XARF] report, as
described in Section 3.5.1.
3.5. Feedback Message
The Feedback Message (sent by Mailbox Provider to the address
provided in the CFBL-Address header field) MUST have a valid [DKIM]
signature. This signature MUST match the [RFC5322].From domain of
the Feedback Message.
If the message does not have the required valid [DKIM] signature, the
Message Originator SHALL NOT process this Feedback Message.
The Feedback Message MUST be a [ARF] or [XARF] report. If the
Message Originator requests it (described in Section 3.5.1), and it
is technically possible for the Mailbox Provider to do so, the
Feedback Message MUST be a [XARF] report, otherwise the Feedback
Message MUST be a [ARF] report.
The third MIME part of the [ARF] or the "Samples" section of the
[XARF] report MUST contain the Message-ID [MAIL] of the received
message. If present, the header field "CFBL-Feedback-ID" of the
received message MUST be added additionally to the third MIME part of
the [ARF] or to "Samples" section of the [XARF] report.
The Mailbox Provider MAY omit or redact, as described in [RFC6590],
all further header fields and/or body to comply with any data-
regulation laws.
3.5.1. XARF Report
A Message Originator wishing to receive a [XARF] report MUST append
"report=xarf" to the CFBL-Address header field (Section 5.1). The
report parameter is separated from the report address by a ";".
The resulting header field would look like the following:
CFBL-Address: fbl@example.com; report=xarf
4. Implementation
4.1. Message Originator
A Message Originator who wishes to use this new mechanism to receive
Feedback Messages MUST include a CFBL-Address header field in their
messages.
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It is RECOMMENDED that these Feedback Messages be processed
automatically. Each Message Originator must decide for themselves
what action to take after receiving a Feedback Message.
The Message Originator MUST take action to address the described
requirements in Section 3.
4.2. Mailbox Provider
A Mailbox Provider who wants to collect user actions that indicate
the message was not wanted and send a Feedback Message to the Message
Originator, they MAY query the CFBL-Address header field and forward
the report to the provided complaint feedback loop address.
The Mailbox Provider MUST validate the DKIM requirements of the
received Message described in Section 3.1 and MUST take action to
address the requirements described in Section 3.5 when sending
Feedback Messages.
5. Header Field Syntax
5.1. CFBL-Address
The following ABNF imports fields, CFWS, CRLF and addr-spec from
[MAIL]. Implementations of the CFBL-Address header field MUST comply
with [RFC6532].
fields =/ cfbl-address
cfbl-address = "CFBL-Address:" CFWS addr-spec
[";" CFWS report-format] CRLF
report-format = %s"report=" (%s"arf" / %s"xarf")
5.2. CFBL-Feedback-ID
The following ABNF imports fields, WSP, CRLF and atext from [MAIL].
fields =/ cfbl-feedback-id
cfbl-feedback-id = "CFBL-Feedback-ID:" CFWS fid CRLF
fid = 1*(atext / ":" / CFWS)
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Whitespace is ignored in the fid value and MUST be ignored when
reassembling the original feedback id.
In particular, when adding the header field the Message Originator
can safely insert CFWS in the fid value in arbitrary places to
conform to line-length limits.
6. Security Considerations
This section discusses possible security issues, and their possible
solutions, of a complaint feedback loop address header field.
6.1. Attacks on the Feedback Loop Address
Like any other email address, a complaint feedback loop address can
be an attack vector for malicious messages. For example, complaint
feedback loop addresses can be flooded with spam. This is an
existing problem with any existing email address and is not created
by this document.
6.2. Automatic Suspension of an Account
Receiving a Feedback Message regarding a Message Author can cause the
Message Author to be unreachable if an automatic account suspension
occurs too quickly. An example: someone sends an invitation to their
friends. For some reason, someone marks this message as spam.
Now, if there is too fast automatic account suspension, the Message
Author's account will be blocked and the Message Author will not be
able to access their emails or is able to send further messages,
depending on the account suspension the Message Originator has
chosen.
Message Originators must take appropriate measures to prevent too
fast account suspensions. Message Originators therefore have -
mostly proprietary - ways to assess the trustworthiness of an
account. For example, Message Originators may take into account the
age of the account and/or any previous account suspension before
suspending an account.
6.3. Enumeration Attacks / Provoking Unsubscription
A malicious person may send a series of spoofed ARF messages to known
complaint feedback loop addresses and attempt to guess a Message-ID/
CFBL-Feedback-ID or any other identifiers. The malicious person may
attempt to mass unsubscribe/suspend if such an automated system is in
place. This is also an existing problem with the current feedback
loop implementation and/or One-Click Unsubscription [RFC8058].
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The Message Originator must take appropriate measures, a
countermeasure would be, that the CFBL-Feedback-ID header field, if
used, use a hard-to-forge component such as a [HMAC] with a secret
key instead of a plaintext string to make an enumeration attack
impossible.
6.4. Data Privacy
The provision of such a header field itself does not pose a data
privacy issue. The resulting ARF/XARF report sent by the Mailbox
Provider to the Message Originator may violate a data privacy law
because it may contain personal data.
This document already addresses some parts of this problem and
describes a data privacy safe way to send a Feedback Message. As
described in Section 3.5, the Mailbox Provider can omit the entire
body and/or header field and send only the required fields. As
recommended in [RFC6590], the Mailbox Provider can also redact the
data in question. Nevertheless, each Mailbox Provider must consider
for itself whether this implementation is acceptable and complies
with existing data privacy laws in their country.
As described in Section 3.5 and in Section 3.3, it is also strongly
RECOMMENDED that the Message-ID and, if used, the CFBL-Feedback-ID.
contain a component that is difficult to forge, such as a [HMAC] that
uses a secret key, rather than a plaintext string. See Section 8.3
for an example.
6.5. Abusing for Validity and Existence Queries
This mechanism could be abused to determine the validity and
existence of an email address, which exhibits another potential data
privacy issue. Now, if the Mailbox Provider has an automatic process
to generate a Feedback Message for a received message, it may not be
doing the mailbox owner any favors. As the Mailbox Provider now
generates an automatic Feedback Message for the received message, the
Mailbox Provider now proves to the Message Originator that this
mailbox exists for sure, because it is based on a manual action of
the mailbox owner.
The receiving Mailbox Provider must take appropriate measures. One
possible countermeasure could be, for example, pre-existing
reputation data, usually proprietary data. Using this data, the
Mailbox Provider can assess the trustworthiness of a Message
Originator and decide whether to send a Feedback Message based on
this information.
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7. IANA Considerations
7.1. CFBL-Address
The IANA is requested to register a new header field, per [RFC3864],
into the "Provisional Message Header Field Names" registry:
Header field name: CFBL-Address
Applicable protocol: mail
Status: provisional
Author/Change controller: Jan-Philipp Benecke <jpb@cleverreach.com>
Specification document: this document
7.2. CFBL-Feedback-ID
The IANA is requested to register a new header field, per [RFC3864],
into the "Provisional Message Header Field Names" registry:
Header field name: CFBL-Feedback-ID
Applicable protocol: mail
Status: provisional
Author/Change controller: Jan-Philipp Benecke <jpb@cleverreach.com>
Specification document: this document
8. Examples
For simplicity the DKIM header field has been shortened, and some
tags have been omitted.
8.1. Simple
Email about the report will be generated:
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Return-Path: <sender@mailer.example.com>
From: Awesome Newsletter <newsletter@example.com>
To: me@example.net
Subject: Super awesome deals for you
CFBL-Address: fbl@example.com; report=arf
CFBL-Feedback-ID: 111:222:333:4444
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@mailer.example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=example.com; s=news;
h=Subject:From:To:Message-ID:CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
Resulting ARF report:
------=_Part_240060962_1083385345.1592993161900
Content-Type: message/feedback-report
Content-Transfer-Encoding: 7bit
Feedback-Type: abuse
User-Agent: FBL/0.1
Version: 0.1
Original-Mail-From: sender@mailer.example.com
Arrival-Date: Tue, 23 Jun 2020 06:31:38 GMT
Reported-Domain: example.com
Source-IP: 192.0.2.1
------=_Part_240060962_1083385345.1592993161900
Content-Type: text/rfc822; charset=UTF-8
Content-Transfer-Encoding: 7bit
Return-Path: <sender@mailer.example.com>
From: Awesome Newsletter <newsletter@example.com>
To: me@example.net
Subject: Super awesome deals for you
CFBL-Address: fbl@example.com; report=arf
CFBL-Feedback-ID: 111:222:333:4444
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@mailer.example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=example.com; s=news;
h=Subject:From:To:Message-ID:CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
------=_Part_240060962_1083385345.1592993161900--
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8.2. Data Privacy Safe Report
Email about the report will be generated:
Return-Path: <sender@mailer.example.com>
From: Awesome Newsletter <newsletter@example.com>
To: me@example.net
Subject: Super awesome deals for you
CFBL-Address: fbl@example.com; report=arf
CFBL-Feedback-ID: 111:222:333:4444
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@mailer.example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=example.com; s=news;
h=Subject:From:To:Message-ID:CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
Resulting ARF report contains only the CFBL-Feedback-ID:
------=_Part_240060962_1083385345.1592993161900
Content-Type: message/feedback-report
Content-Transfer-Encoding: 7bit
Feedback-Type: abuse
User-Agent: FBL/0.1
Version: 0.1
Original-Mail-From: sender@mailer.example.com
Arrival-Date: Tue, 23 Jun 2020 06:31:38 GMT
Reported-Domain: example.com
Source-IP: 2001:DB8::25
------=_Part_240060962_1083385345.1592993161900
Content-Type: text/rfc822-headers; charset=UTF-8
Content-Transfer-Encoding: 7bit
CFBL-Feedback-ID: 111:222:333:4444
------=_Part_240060962_1083385345.1592993161900--
8.3. Data Privacy Safe Report with HMAC
Email about the report will be generated:
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Return-Path: <sender@mailer.example.com>
From: Awesome Newsletter <newsletter@example.com>
To: me@example.net
Subject: Super awesome deals for you
CFBL-Address: fbl@example.com; report=arf
CFBL-Feedback-ID: 3789e1ae1938aa2f0dfdfa48b20d8f8bc6c21ac34fc5023d
63f9e64a43dfedc0
Message-ID: <a37e51bf-3050-2aab-1234-543a0828d14a@mailer.example.com>
Content-Type: text/plain; charset=utf-8
DKIM-Signature: v=1; a=rsa-sha256; d=example.com; s=news;
h=Subject:From:To:Message-ID:CFBL-Feedback-ID:CFBL-Address;
This is a super awesome newsletter.
Resulting ARF report contains only the CFBL-Feedback-ID:
------=_Part_240060962_1083385345.1592993161900
Content-Type: message/feedback-report
Content-Transfer-Encoding: 7bit
Feedback-Type: abuse
User-Agent: FBL/0.1
Version: 0.1
Original-Mail-From: sender@mailer.example.com
Arrival-Date: Tue, 23 Jun 2020 06:31:38 GMT
Reported-Domain: example.com
Source-IP: 2001:DB8::25
------=_Part_240060962_1083385345.1592993161900
Content-Type: text/rfc822-headers; charset=UTF-8
Content-Transfer-Encoding: 7bit
CFBL-Feedback-ID: 3789e1ae1938aa2f0dfdfa48b20d8f8bc6c21ac34fc5023d
63f9e64a43dfedc0
------=_Part_240060962_1083385345.1592993161900--
9. Acknowledgments
Technical and editorial reviews were provided by the colleagues at
CleverReach, the colleagues at Certified Senders Alliance and eco.de,
Arne Allisat, Tobias Herkula and Levent Ulucan (1&1 Mail & Media) and
Sven Krohlas (BFK Edv-consulting).
10. References
10.1. Normative References
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Internet-Draft CFBL Address Header May 2023
[ARF] Shafranovich, Y., Levine, J., and M. Kucherawy, "An
Extensible Format for Email Feedback Reports", RFC 5965,
DOI 10.17487/RFC5965, August 2010,
<https://www.rfc-editor.org/rfc/rfc5965>.
[DKIM] Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
"DomainKeys Identified Mail (DKIM) Signatures", STD 76,
RFC 6376, DOI 10.17487/RFC6376, September 2011,
<https://www.rfc-editor.org/rfc/rfc6376>.
[MAIL] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/rfc/rfc5322>.
[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>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/rfc/rfc5234>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/rfc/rfc5322>.
[RFC6449] Falk, J., Ed., "Complaint Feedback Loop Operational
Recommendations", RFC 6449, DOI 10.17487/RFC6449, November
2011, <https://www.rfc-editor.org/rfc/rfc6449>.
[RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized
Email Headers", RFC 6532, DOI 10.17487/RFC6532, February
2012, <https://www.rfc-editor.org/rfc/rfc6532>.
[RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
RFC 7405, DOI 10.17487/RFC7405, December 2014,
<https://www.rfc-editor.org/rfc/rfc7405>.
[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>.
[XARF] Abusix, "eXtended Abuse Reporting Format",
Web https://github.com/abusix/xarf.
10.2. Informative References
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[HMAC] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<https://www.rfc-editor.org/rfc/rfc2104>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/rfc/rfc3864>.
[RFC6590] Falk, J., Ed. and M. Kucherawy, Ed., "Redaction of
Potentially Sensitive Data from Mail Abuse Reports",
RFC 6590, DOI 10.17487/RFC6590, April 2012,
<https://www.rfc-editor.org/rfc/rfc6590>.
[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>.
Author's Address
Jan-Philipp Benecke
CleverReach GmbH & Co. KG
Schafjueckenweg 2
26180 Rastede
Germany
Phone: +49 4402 97390-16
Email: jpb@cleverreach.com
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