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Internet Engineering Task Force (IETF)
Request for Comments: 6430
Category: Standards Track
ISSN: 2070-1721
K. Li
B. Leiba
Huawei Technologies
November 2011

Email Feedback Report Type Value: not-spam

Abstract

This document defines a new Abuse Reporting Format (ARF) feedback report type value: "not-spam". It can be used to report an email message that was mistakenly marked as spam.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6430.

Copyright Notice

Copyright © 2011 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://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. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................2
      1.1. Discussion .................................................2
   2. Feedback Report Type: not-spam ..................................3
   3. Example .........................................................3
   4. Security Considerations .........................................5
   5. IANA Considerations .............................................6
   6. Acknowledgements ................................................6
   7. References ......................................................6
      7.1. Normative References .......................................6
      7.2. Informative References .....................................6

1. Introduction

In RFC 5965 [RFC5965], an Abuse Reporting Format (ARF) is defined for reporting email abuse. Currently, two feedback report types are defined that are related to the spam problem and that can be used to report abusive or fraudulent email messages:

  • abuse: indicates unsolicited email or some other kind of email abuse.
  • fraud: indicates some kind of fraud or phishing activity.

This specification defines a new feedback report type: "not-spam". It can be used to report a message that was mistakenly marked as spam.

1.1. Discussion

In some cases, the email client receives an email message that was incorrectly tagged as spam, perhaps by the email system, or accidentally by the user. The email client accepts the end user's "not-spam" report instruction, retrieves information related to the message, and reports this email as not-spam to the email operator. When the email operator receives the report, it can determine what action is appropriate for the particular message and user. (The requirement for a not-spam report type is from the Open Mobile Alliance (OMA) Spam Report Requirement Document [OMA-SpamRep-RD].)

For example, in response to a "not-spam" report, the email system can remove the spam tag or otherwise reclassify the message, possibly preventing similar email for this user from being marked as spam in the future. The report can be used to adjust the training of an automated classifier. After processing the report, the email operator might send a notification to the email client about the processing result (for example, by moving the message from one mailbox to another, such as from "Junk" to "Inbox").

In most cases, "not-spam" reports will probably not be taken on their own, but will be considered along with other information, analysis of the message, etc. Because different users have different needs and different views of what constitutes spam, reports from one user might or might not be applicable to others. And because users might sometimes press a "report not spam" button accidentally, immediate strong action, such as marking all similar messages as "good" based on a single report, is probably not the right approach. Recipients of "not-spam" reports need to consider what's right in their environments.

There are anti-spam systems that use (non-standard) "not spam" feedback today. All of them take the reports and mix them with other spam reports and other data, using their own algorithms, to determine appropriate action. In no case do the existing systems use a "not spam" report as an immediate, automatic override.

The feedback types "abuse" and "not-spam" can be taken as opposites. A mistaken "not-spam" report could be countermanded by a subsequent "abuse" report from the same user, and an operator could consider collected reports of "abuse" and "not-spam" in making future assessments.

2. Feedback Report Type: not-spam

This document defines a new feedback report type, "not-spam", which extends the Email Feedback Reports specification [RFC5965].

In the first MIME part of the feedback report message, the end user or the email client can add information to indicate why the message is not considered as spam -- for example, because the originator or its domain is well known.

3. Example

In the example, Joe, a pharmaceuticals sales representative, has received a message about discount pharmaceuticals. Because that is a frequent subject of spam email, the message has been marked as spam -- incorrectly, in this case. Joe has reported it as "not-spam", and this is an example of the report, shortened (the "[...etc...]" part) for presentation here.

Note that the message has been signed using DomainKeys Identified Mail (DKIM) [RFC6376] -- a good security practice as suggested in Section 8.2 of RFC 5965 [RFC5965]. 

      DKIM-Signature: v=1; a=rsa-sha256; s=abuse; d=example.com;
        c=simple/simple; q=dns/txt; i=abusedesk@example.com;
        h=From:Date:Subject:To:Message-ID:MIME-Version:Content-Type;
        bh=iF4dMNYs/KepE0HuwfukJCDyjkduUzZFiaHqO9DMIPU=;
        b=e+BF8DCHFGqCp7/pExleNz7pVaLEoT+uWj/8H9DoZpxFI1vNnCTDu14w5v
          ze4mqJkldudVI0JspsYHTYeomhPklCV4F95GfwpM5W+ziUOv7AySTfygPW
          EerczqZwAK88//oaYCFXq3XV9T/z+zlLp3rrirKGmCMCPPcbdSGv/Eg=
      From: <abusedesk@example.com>
      Date: Thu, 8 Mar 2005 17:40:36 EDT
      Subject: FW: Discount on pharmaceuticals
      To: <abuse@example.net>
      Message-ID: <20030712040037.46341.5F8J@example.com>
      MIME-Version: 1.0
      
      Content-Type: multipart/report; report-type=feedback-report;
           boundary="part1_13d.2e68ed54_boundary"
      
      --part1_13d.2e68ed54_boundary
      Content-Type: text/plain; charset="US-ASCII"
      Content-Transfer-Encoding: 7bit

This is an email abuse report for an email message received from IP 192.0.2.1 on Thu, 8 Mar 2005 14:00:00 EDT.
For more information about this format please see http://tools.ietf.org/html/rfc5965
Comment: I sell pharmaceuticals, so this is not spam for me. 

      --part1_13d.2e68ed54_boundary
      Content-Type: message/feedback-report
      
      Feedback-Type: not-spam
      User-Agent: SomeGenerator/1.0
      Version: 1
      
      --part1_13d.2e68ed54_boundary
      Content-Type: message/rfc822
      Content-Disposition: inline
      Received: from mailserver.example.net
           (mailserver.example.net [192.0.2.1])
           by example.com with ESMTP id M63d4137594e46;
           Thu, 08 Mar 2005 14:00:00 -0400
      From: <someone@example.net>
      To: <Undisclosed Recipients>
      Subject: Discount on pharmaceuticals
      MIME-Version: 1.0
      Content-type: text/plain
      Message-ID: 8787KJKJ3K4J3K4J3K4J3.mail@example.net
      Date: Thu, 02 Sep 2004 12:31:03 -0500
      
      Hi, Joe.  I got a lead on a source for discounts on
      pharmaceuticals, and I thought you might be interested.
      [...etc...]
      --part1_13d.2e68ed54_boundary--

Example 1: not-spam Report

4. Security Considerations

All of the security considerations from the Email Feedback Reports specification [RFC5965] are inherited here. In addition, the Email Feedback Reports Applicability Statement [MARF-AS] contains important information about trust relationships and other security- and integrity-related aspects of accepting abuse feedback.

In particular, not-spam reports will likely be used in an attack on a filtering system, reporting true spam as "not-spam". Even in absence of malice, some not-spam reports might be made in error, or will only apply to the user sending the report. Operators need to be careful in trusting such reports, beyond their applicability to the specific user in question.

5. IANA Considerations

IANA has registered the newly defined feedback type name: "not-spam", according to the instructions in Section 7.3 of the base specification [RFC5965].

The following has been added to the "Feedback Report Type Values" registry: 

   Feedback Type Name:  not-spam
   
   Description:  Indicates that the entity providing the report does not
      consider the message to be spam.  This may be used to correct a
      message that was incorrectly tagged or categorized as spam.
   
   Published in:  this document
   
   Status:  current

6. Acknowledgements

The authors would like to thank Murray S. Kucherawy and Bert Greevenbosch for their discussion and review, and J.D. Falk for suggesting some explanatory text.

7. References

7.1. Normative References

   [RFC5965]  Shafranovich, Y., Levine, J., and M. Kucherawy, "An
              Extensible Format for Email Feedback Reports", RFC 5965,
              August 2010.

7.2. Informative References

   [MARF-AS]  Falk, J., "Creation and Use of Email Feedback Reports: An
              Applicability Statement for the Abuse Reporting Format
              (ARF)", Work in Progress, September 2011.

[OMA-SpamRep-RD] 

              Open Mobile Alliance, "Mobile Spam Reporting
              Requirements", Candidate Version 1.0 OMA-RD-SpamRep-V1_0-
              20101123-C, November 2010, <http://
              www.openmobilealliance.org/Technical/release_program/docs/
              SpamRep/V1_0-20101123-C/
              OMA-RD-SpamRep-V1_0-20101123-C.pdf>.
   
   [RFC6376]  Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
              "DomainKeys Identified Mail (DKIM) Signatures", RFC 6376,
              September 2011.

Authors' Addresses

   Kepeng Li
   Huawei Technologies
   Huawei Base, Bantian, Longgang District
   Shenzhen, Guangdong  518129
   P.R. China
   
   Phone: +86-755-28974289
   EMail: likepeng@huawei.com

Barry Leiba
Huawei Technologies 

   Phone: +1 646 827 0648
   EMail: barryleiba@computer.org
   URI:   http://internetmessagingtechnology.org/