Creation and Use of Email Feedback Reports: An Applicability Statement for the Abuse Reporting Format (ARF)
Author(s): Murray Kucherawy, Return Path
RFC 5965 defines an extensible, machine-readable format intended for mail operators to report feedback about received email to other parties. This Applicability Statement describes common methods for utilizing this format for reporting both abuse and authentication failure events....
MARF Working Group J. Falk Internet-Draft Return Path Updates: 5965 (if approved) M. Kucherawy, Ed. Intended status: Standards Track Cloudmark Expires: October 27, 2012 April 25, 2012 Creation and Use of Email Feedback Reports: An Applicability Statement for the Abuse Reporting Format (ARF) draft-ietf-marf-as-16 Abstract RFC 5965 defines an extensible, machine-readable format intended for mail operators to report feedback about received email to other parties. This Applicability Statement describes common methods for utilizing this format for reporting both abuse and authentication failure events. Mailbox Providers of any size, mail sending entities, and end users can use these methods as a basis to create procedures that best suit them. Some related optional mechanisms are also discussed. 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 http://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 October 27, 2012. Copyright Notice Copyright (c) 2012 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 Falk & Kucherawy Expires October 27, 2012 [Page 1] Internet-Draft ARF AS April 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Solicited and Unsolicited Reports . . . . . . . . . . . . . . 4 4. Generating And Handling Solicited Abuse Reports . . . . . . . 4 4.1. General Considerations for Feedback Providers . . . . . . 5 4.2. Where To Send Reports . . . . . . . . . . . . . . . . . . 5 4.3. What To Put In Reports . . . . . . . . . . . . . . . . . . 5 4.4. General Considerations for Feedback Consumers . . . . . . 5 4.5. What To Expect . . . . . . . . . . . . . . . . . . . . . . 6 4.6. What To Do With Reports . . . . . . . . . . . . . . . . . 6 5. Generating and Handling Unsolicited Abuse Reports . . . . . . 6 5.1. General Considerations . . . . . . . . . . . . . . . . . . 6 5.2. When To Generate Reports . . . . . . . . . . . . . . . . . 7 5.3. Where To Send Reports . . . . . . . . . . . . . . . . . . 7 5.4. What To Put In Reports . . . . . . . . . . . . . . . . . . 8 5.5. What To Do With Reports . . . . . . . . . . . . . . . . . 9 6. Generating Automatic Authentication Failure Reports . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8.1. In Other Documents . . . . . . . . . . . . . . . . . . . . 11 8.2. Forgeries . . . . . . . . . . . . . . . . . . . . . . . . 11 8.3. Amplification Attacks . . . . . . . . . . . . . . . . . . 11 8.4. Automatic Generation . . . . . . . . . . . . . . . . . . . 12 8.5. Reporting Multiple Incidents . . . . . . . . . . . . . . . 12 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 10.1. Normative References . . . . . . . . . . . . . . . . . . . 13 10.2. Informative References . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Falk & Kucherawy Expires October 27, 2012 [Page 2] Internet-Draft ARF AS April 2012 1. Introduction The Abuse Reporting Format (ARF) was initially developed for two very specific use cases. Initially, it was intended to be used for reporting feedback between large email operators, or from large email operators to end user network access operators, any of whom could be presumed to have automated abuse-handling systems. Secondarily, it is used by those same large mail operators to send those same reports to other entities, including those involved in sending bulk email for commercial purposes. In either case, the reports would be triggered by direct end user action such as clicking on a "report spam" button in their email client. Though other uses for the ARF format defined in [RFC 5965] have been discussed (and may be documented similarly in the future), abuse remains the primary application, with a small amount of adoption of extensions that enable authentication failure reporting. This Applicability Statement provides direction for using the Abuse Reporting Format (ARF) in both contexts. It also includes some statements about the use of ARF in conjunction with other email technologies. The purpose for reporting abusive messages is to stop recurrences. The methods described in this document focus on automating abuse reporting as much as practical, so as to minimize the work of a site's abuse team. There are further reasons why abuse feedback generation is worthwhile, such as instruction of mail filters or reputation trackers, or to initiate investigations of particularly egregious abuses. These other applications are not discussed in this memo. Further introduction to this topic may be found in [RFC6449], which is effectively an Applicability Statement written outside of the IETF and thus never achieved IETF consensus. Much of the content for that document was input to this one. At the time of publication of this document, five feedback types are registered. This document only discusses two of them ("abuse" and "auth-failure") as they are seeing sufficient use in practice that applicability statements can be made about them. The others, i.e., "fraud" [RFC 5965] and "not-spam" [RFC6430], are either too new or too seldomly used to be included here. 1.1. Discussion [RFC Editor: please remove this section prior to publication.] Falk & Kucherawy Expires October 27, 2012 [Page 3] Internet-Draft ARF AS April 2012 This document is being discussed within the IETF MARF Working Group, on the email@example.com mailing list. 2. Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119], and are intended to replace the Requirement Levels described in Section 3.3 of [RFC2026]. Some of the terminology used in this document is taken from [RFC5598]. "Mailbox Provider" refers to an organization that accepts, stores, and offers access to [RFC5322] messages ("email messages") for end users. Such an organization has typically implemented SMTP ([RFC5321]), and might provide access to messages through IMAP ([RFC3501]), POP ([RFC1939]), a proprietary interface designed for HTTP ([RFC2616]), or a proprietary protocol. 3. Solicited and Unsolicited Reports The original application of [RFC 5965], and still by far the most common, is when two mail systems make a private agreement to exchange abuse reports, usually reports due to recipients manually reporting messages as spam. We refer to these as solicited reports. Other uses for ARF involve such reports sent between parties that don't know each other. These unsolicited reports are sent without prior arrangement between the parties as to the context and meaning of the reports, so the constraints on how these unsolicited reports need to be structured such that the reports generated are likely to be useful to the recipient, to what address(es) they can usefully be sent, what issues the can be used to report, and how they can be handled by the receiver of the report are very different. The two cases are covered separately in following sections. 4. Generating And Handling Solicited Abuse Reports [The numbered items in these subsections are not intended to be in a paricular sequence. The numbers are here during document development to make it easier to identify the items for discussion, and will be removed before publication.] Falk & Kucherawy Expires October 27, 2012 [Page 4] Internet-Draft ARF AS April 2012 4.1. General Considerations for Feedback Providers 1. A Mailbox Provider receives reports of abusive or unwanted mail from its users, most often by providing a "report spam" button (or similar nomenclature) in the MUA (Mail User Agent). The method of transferring this message and any associated metadata from the MUA to the Mailbox Provider's ARF processing system is not defined by any standards document, but is discussed further in Section 3.2 of [RFC6449]. Policy concerns related to the collection of this data are discussed in Section 3.4 of [RFC6449]. 2. To implement the recommendations of this memo, the reports are formatted per [RFC 5965], and transmitted as an email message ([RFC5322]), typically using SMTP ([RFC5321]). 3. Ongoing maintenance of an ARF processing system is discussed in Section 3.6 of [RFC6449]. 4.2. Where To Send Reports 1. The Mailbox Provider SHOULD NOT send reports to addresses that have not explicitly requested them. A valid deviation might be the result of local policy instructions. The process whereby such parties may request the reports is discussed in Section 3.5 of [RFC6449]. 4.3. What To Put In Reports 1. The reports SHOULD use "Feedback-Type: abuse", for its type. Although a Mailbox Provider generating the reports can use other types appropriate to the nature of the abuse being reported, the operator receiving the reports might not treat different feedback types differently. 2. The following fields are optional in [RFC 5965], but SHOULD be used in this context when their corresponding values are available: Original-Mail-From, Arrival-Date, Source-IP, Original- Rcpt-To. Other optional fields can be included, as the implementer feels is appropriate. 3. User-identifiable data MAY be obscured as described in [RFC6590]. 4.4. General Considerations for Feedback Consumers 1. ARF report streams are established proactively between Feedback Providers and Feedback Consumers. Recommendations for preparing to make that request are discussed in Section 4.1 of [RFC6449]. 2. Operators MUST be able to accept ARF [RFC 5965] reports as email messages [RFC5322] over SMTP [RFC5321]. These and other types of email messages that can be received are discussed in Section 4.2 of [RFC6449]. Falk & Kucherawy Expires October 27, 2012 [Page 5] Internet-Draft ARF AS April 2012 3. Recipients of feedback reports that are part of formal feedback arrangements have to be capable of handling large volumes of reports. This could require automation of report processing. Discussion of this can be found in Section 4.4 of [RFC6449]. 4.5. What To Expect 1. The list of vaild Feedback-Types is defined in [RFC 5965], which created an IANA registry for valid values to allow for extensions. However, an automated report processing system MUST NOT reject (in the SMTP sense) a report based solely on an unknown Feedback-Type, to allow for handling of new types that are not yet supported. The automated system can simply set reports of unknown types aside for manual handling. However, Mailbox Providers might only make use of the "abuse" Feedback- Type. Therefore, report receivers might be required to do additional analysis to separate different types of abuse reports after receipt if they do not have prior specific knowledge of the sender of the report. 2. Reports receivers MUST accept reports that have obscured their user-identifiable data as described in [RFC6590]. That document also discusses the handling of such reports. This technique is also discussed in Section 4.4 of [RFC6449]. 4.6. What To Do With Reports 1. Section 4.3 of [RFC6449] discusses actions that mail operators might take upon receiving a report (or multiple reports). 5. Generating and Handling Unsolicited Abuse Reports [The numbered items in these subsections are not intended to be in a paricular sequence. The numbers are here during document development to make it easier to identify the items for discussion, and will be removed before publication.] 5.1. General Considerations 1. It is essential for report recipients to be capable of throttling reports being sent to avoid damage to their own installations. Therefore, Feedback Providers MUST provide a way for report recipients to request that no further reports be sent. Unfortunately, no standardized mechanism for such requests exists to date, and all existing mechanisms for meeting this requirement are out-of-band. Falk & Kucherawy Expires October 27, 2012 [Page 6] Internet-Draft ARF AS April 2012 2. Message authentication is generally a good idea, but it is especially important to encourage credibility of and thus response to unsolicited reports. Therefore, as with any other message, Feedback Providers sending unsolicited reports SHOULD send reports that they believe will pass Sender Policy Framework ([RFC4408]) and/or DomainKeys Identified Mail ([RFC6376]) checks. 5.2. When To Generate Reports 1. Handling of unsolicited reports has a significant cost to the report receiver. Senders of unsolicited reports, especially those sending large volumes of them automatically SHOULD NOT send reports that cannot be used as a basis for action by the recipient, whether this is due to the report being sent about an incident that is not abuse-related, the report being sent to an email address that won't result in action, or the content or format of the report being hard for the recipient to read or use. 2. Feedback Providers SHOULD NOT report all mail sent from a particular sender merely because some of it is determined to be abusive. 3. Mechanical reports of mail that "looks like" spam, based solely on the results of inline content analysis tools, SHOULD NOT be sent since, because of their subjective nature, they are unlikely to provide a basis for the recipient to take action. Complaints generated by end users about mail that is determined by them to be abusive, or mail delivered to "spam trap" or "honeypot" addresses, are far more likely to be accurate and MAY be sent. 4. If a Feedback Provider applies the Sender Policy Framework [RFC4408] to arriving messages, a report SHOULD NOT be generated to the RFC5321.MailFrom domain if the SPF evaluation produced a "Fail", "SoftFail", "TempError" or "PermError" report, as no reliable assertion or assumption can be made that use of the domain was authorized. A valid exception would be specific knowledge that the SPF result is not definitive for that domain under those circumstances (for example, a message that is also signed using DomainKeys Identified Mail (DKIM, [RFC6376]) by the same domain, and that signature validates). 5.3. Where To Send Reports 1. Rather than generating feedback reports themselves, MUAs SHOULD make abuse reports back to their mailbox providers so that they can generate and send ARF messages on behalf of end users (see Section 3.2 of [RFC6449]). This allows centralized processing and tracking of reports, and provides training input to filtering systems. There is, however, no standard mechanism for this signaling between MUAs and mailbox providers to trigger abuse reports. Falk & Kucherawy Expires October 27, 2012 [Page 7] Internet-Draft ARF AS April 2012 2. Feedback Providers SHOULD NOT send reports to recipients that are uninvolved or only peripherally involved. For example, they SHOULD NOT send reports to the operator of every Autonomous System in the path between the apparent originating system and the operator generating the report. Instead, they need to send reports to recipients that are both responsible for the messages and are able to do something about them. 3. Deciding where to send an unsolicited report will typically rely on heuristics. Abuse addresses in WHOIS ([RFC3912]) records of the IP address relaying the subject message and/or of the domain name found in the results of a PTR ("reverse lookup") query on that address are likely reasonable candidates, as is the abuse@domain role address (see [RFC2142]) of related domains. Unsolicited reports SHOULD NOT be sent to email addresses that are not clearly intended to handle abuse reports. Legitimate candidates include those found in WHOIS records or on a web site that either are explicitly described as an abuse contact, or are of the form "abuse@domain". 4. Where an abusive message is authenticated using a domain-level authentication technology such as DKIM ([RFC6376]) or SPF ([RFC4408]), the domain that has been verified by the authentication mechanism is often a reasonable candidate for receiving feedback about the message. For DKIM, though, while the authenticated domain has some responsibility for the mail sent, it can be a poor contact point for abuse issues (for example, it could represent the message's author but not its sender, it could identify the bad actor responsible for the message, or it could refer to a domain that cannot receive mail at all). 5. Often, unsolicited reports will have no meaning if sent to abuse reporting addresses belonging to the abusive parties themselves. In fact, it is possible that such reports might reveal information about complainants. Reports SHOULD NOT be sent to such addresses if they can be identified beforehand, except where the abusive party is known to be responsive to such reports. 5.4. What To Put In Reports 1. Reports SHOULD use "Feedback-Type: abuse", but can use other types as appropriate. However, the Mailbox Provider generating the reports cannot assume that the operator receiving the reports will treat different Feedback-Types differently. 2. Reports SHOULD include the following optional fields whenever their corresponding values are available and applicable to the report: Original-Mail-From, Arrival-Date, Source-IP, Original- Rcpt-To. Other optional fields can be included, as the implementer feels is appropriate. Falk & Kucherawy Expires October 27, 2012 [Page 8] Internet-Draft ARF AS April 2012 3. Experience suggests use of ARF is advisable in most contexts. Automated recipient systems can handle abuse reports sent in ARF format at least as well as any other format such as plain text, with or without a copy of the message attached. That holds even for systems that did not request ARF format reports, assuming such reports are generated considering the possibility of recipients that don't use automated ARF parsing. Anyone sending unsolicited reports in ARF format can legitimately presume that some recipients will only be able to access the human readable (first, text/plain) part of it, and SHOULD include all information needed also in this part. Further, they SHOULD ensure that the report is readable when viewed as plain text, to give low-end ticketing systems as much assistance as possible. In extreme cases, failure to take these steps may result in the report being discarded or ignored. 5.5. What To Do With Reports 1. Receivers of unsolicited reports can take advantage of the standardized parts of the ARF format to automate processing. Independent of the sender of the report, they can improve processing by separating valid from invalid reports by, for example, looking for references to IP address ranges, domains, and mailboxes for which the recipient organization is responsible in the copy of the reported message, and by correlating multiple reports of similar messages to identify bulk email senders. 2. Per Section 4.4 of [RFC6449], a network service provider MAY use ARF data for automated forwarding of feedback messages to the originating customer. 3. Published abuse mailbox addresses SHOULD NOT reject non-ARF messages based solely on the format, as generation of ARF messages can occasionally be unavailable or not applicable. Deviation from this requirement could be done due to local policy decisions regarding other message criteria. 4. Although [RFC6449] suggests that replying to feedback is not useful, in the case of receipt of ARF reports where no feedback arrangement has been established, a non-automated reply might be desirable to indicate what action resulted from the complaint, heading off more severe filtering by the Feedback Provider. In addition, using an address that cannot receive replies precludes any requests for additional information, and increases the likelihood that further reports will be discarded or blocked. Thus, a Feedback Provider sending unsolicited reports SHOULD NOT generate reports for which a reply cannot be received. Where an unsolicited report results in the establishment of contact with a responsible and responsive party, this can be saved for future complaint handling and possible establishment of a formal (solicited) feedback arrangement. See Section 3.5 of [RFC6449] Falk & Kucherawy Expires October 27, 2012 [Page 9] Internet-Draft ARF AS April 2012 for a discussion of establishment of feedback arrangements. 6. Generating Automatic Authentication Failure Reports [These numbered items are not intended to be in a paricular sequence. The numbers are here during document development to make it easier to identify the items for discussion, and will be removed before publication.] There are some cases where report generation is caused by automation rather than user request. A specific example of this is reporting, using the ARF format (or extensions to it), of messages that fail particular message authentication checks. Examples of this include [I-D.IETF-MARF-DKIM-REPORTING] and [I-D.IETF-MARF-SPF-REPORTING]. The considerations presented below apply in those cases. The applicability statement for this use case is somewhat smaller as many of the issues associated with abuse reports are not relevant to reports about authentication failures. 1. Automatic feedback generators MUST select actual message recipients based on data provided by willing report receivers. In particular, recipients MUST NOT be selected using heuristics. 2. If the message under evaluation by the Verifier is an ARF ([RFC 5965]) message, a report MUST NOT be automatically generated. 3. The message for a new report sent via SMTP MUST be constructed so as to avoid amplification attacks, deliberate or otherwise. The envelope sender address of the report MUST be chosen so that these reports will not generate mail loops. Similar to Section 2 of [RFC3464], the envelope sender address of the report MUST be chosen to ensure that no feedback reports will be issued in response to the report itself. Therefore, when an SMTP transaction is used to send a report, the MAIL FROM command SHOULD use the NULL reverse-path, i.e., "MAIL FROM:<>". An exception to this would be the use of a reverse-path selected such that SPF checks on the report will pass; in such cases, the operator will need to make provisions to avoid the amplification attack or mail loop via other means. 4. Reports SHOULD use "Feedback-Type: auth-failure", but MAY use other types as appropriate. However, the Mailbox Provider generating the reports cannot assume that the operator receiving the reports will treat different Feedback-Types differently. 5. These reports SHOULD include the following optional fields, although they are optional in [RFC 5965], whenever their corresponding values are available: Original-Mail-From, Arrival- Date, Source-IP, Original-Rcpt-To. Other optional fields can be Falk & Kucherawy Expires October 27, 2012 [Page 10] Internet-Draft ARF AS April 2012 included, as the implementer feels is appropriate. 7. IANA Considerations [RFC Editor: please remove this section prior to publication.] This document has no IANA actions. 8. Security Considerations 8.1. In Other Documents Implementers are strongly urged to review, at a minimum, the Security Considerations sections of [RFC 5965] and [RFC6449]. 8.2. Forgeries Feedback Providers that relay user complaints directly, rather than by reference to a stored message (e.g., IMAP or POP), could be duped into sending a complaint about a message that the complaining user never actually received, as an attack on the purported originator of the falsified message. Feedback Providers need to be resilient to such attack methods. Also, these reports may be forged as easily as ordinary Internet electronic mail. User agents and automatic mail handling facilities (such as mail distribution list exploders) that wish to make automatic use of reports of any kind should take appropriate precautions to minimize the potential damage from denial-of-service attacks. Perhaps the simplest means of mitigating this threat is to assert that these reports should themselves be signed with something like DKIM and/or authorized by something like SPF. Note, however, that if there is a problem with the email infrastructure at either end, DKIM and/or SPF may result in reports that aren't trusted or even accepted by their intended recipients, so it is important to make sure those components are properly configured. Use of both technologies in tandem can resolve this concern to a degree since they generally have disjoint failure modes. 8.3. Amplification Attacks Failure to comply with the recommendations regarding selection of the envelope sender can lead to amplification denial-of-service attacks. This is discussed in Section 6 as well as in [RFC3464]. Falk & Kucherawy Expires October 27, 2012 [Page 11] Internet-Draft ARF AS April 2012 8.4. Automatic Generation ARF ([RFC 5965]) reports have historically been generated individually as a result of some kind of human request, such as someone clicking a "Report Abuse" button in a mail reader. In contrast, the mechanisms described in some extension documents (i.e., [I-D.IETF-MARF-DKIM-REPORTING] and [I-D.IETF-MARF-SPF-REPORTING]) are focused around automated reporting. This obviously implies the potential for much larger volumes or higher frequency of messages, and thus greater mail system load (both for Feedback Providers and report receivers). Those mechanisms are primarily intended for use in generating reports to aid implementers of DKIM ([RFC6376]), ADSP ([RFC5617]), and SPF ([RFC4408]), and other related protocols during development and debugging. They are not generally intended for prolonged forensic use, specifically because of these load concerns. However, extended use is possible by ADMDs that want to keep a close watch for fraud or infrastructure problems. It is important to consider the impact of doing so on both Feedback Providers and the requesting ADMDs. A sender requesting these reports can cause its mail servers to be overwhelmed if it sends out signed messages whose signatures fail to verify for some reason, provoking a large number of reports from Feedback Providers. Similarly, a Feedback Provider could be overwhelmed by a large volume of messages requesting reports whose signatures fail to validate, as those now need to send reports back to the signer. Limiting the rate of generation of these messages may be appropriate but threatens to inhibit the distribution of important and possibly time-sensitive information. In general ARF feedback loop terms, it is often suggested that Feedback Providers only create these (or any) ARF reports after an out-of-band arrangement has been made between two parties. These extension mechanisms then become ways to adjust parameters of an authorized abuse report feedback loop that is configured and activated by private agreement rather than starting to send them automatically based solely on data found in the messages, which may have unintended consequences. 8.5. Reporting Multiple Incidents If it is known that a particular host generates abuse reports upon certain incidents, an attacker could forge a high volume of messages that will trigger such a report. The recipient of the report could then be innundated with reports. This could easily be extended to a Falk & Kucherawy Expires October 27, 2012 [Page 12] Internet-Draft ARF AS April 2012 distributed denial-of-service attack by finding a number of report- generating servers. The incident count referenced in ARF ([RFC 5965]) provides a limited form of mitigation. The host generating reports can elect to send reports only periodically, with each report representing a number of identical or nearly-identical incidents. One might even do something inverse-exponentially, sending reports for each of the first ten incidents, then every tenth incident up to 100, then every 100th incident up to 1000, etc., until some period of relative quiet after which the limitation resets. The use of this for "nearly-identical" incidents in particular causes a degradation in reporting quality, however. If for example a large number of pieces of spam arrive from one attacker, a reporting agent could decide only to send a report about a fraction of those messages. While this averts a flood of reports to a system administrator, the precise details of each incident are similarly not sent. Other rate limiting provisions might be considered, including detection of a temporary failure response from the report destination and thus halting report generation to that destination for some period, or simply imposing or negotiating a hard limit on the number of reports to be sent to a particular receiver in a given time frame. 9. Acknowledgements The author and editor wish to thank Steve Atkins, John Levine, Shmuel Metz, S. Moonesamy, and Alessandro Vesely for their contributions to this memo. All of the Best Practices referenced by this document are found in [RFC6449], written within the Collaboration Committee of the Messaging Anti-Abuse Working Group (MAAWG). Finally, the original author wishes to thank the doctors and staff at the University of Texas MD Anderson Cancer Center for doing what they do. 10. References 10.1. Normative References [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Falk & Kucherawy Expires October 27, 2012 [Page 13] Internet-Draft ARF AS April 2012 [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC5321, October 2008. [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC5322, October 2008. [RFC5598] Crocker, D., "Internet Mail Architecture", RFC5598, July 2009. [RFC 5965] Shafranovich, Y., Levine, J., and M. Kucherawy, "An Extensible Format for Email Feedback Reports", RFC 5965, August 2010. 10.2. Informative References [I-D.IETF-MARF-DKIM-REPORTING] Kucherawy, M., "Extensions to DKIM for Failure Reporting", draft-ietf-marf-dkim-reporting (work in progress), January 2012. [I-D.IETF-MARF-SPF-REPORTING] Kitterman, S., "SPF Authentication Failure Reporting using the Abuse Report Format", draft-ietf-marf-spf-reporting (work in progress), January 2012. [RFC1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3", STD 53, RFC1939, May 1996. [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC2026, October 1996. [RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND FUNCTIONS", RFC2142, May 1997. [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC2616, June 1999. [RFC3464] Moore, K. and G. Vaudreuil, "An Extensible Message Format for Delivery Status Notifications", RFC3464, January 2003. [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1", RFC3501, March 2003. [RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC3912, September 2004. Falk & Kucherawy Expires October 27, 2012 [Page 14] Internet-Draft ARF AS April 2012 [RFC4408] Wong, M. and W. Schlitt, "Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1", RFC4408, April 2006. [RFC5617] Allman, E., Fenton, J., Delany, M., and J. Levine, "DomainKeys Identified Mail (DKIM) Author Domain Signing Practices (ADSP)", RFC5617, August 2009. [RFC6376] Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys Identified Mail (DKIM) Signatures", RFC6376, September 2011. [RFC6430] Li, K. and B. Leiba, "Email Feedback Report Type Value: not-spam", RFC6430, November 2011. [RFC6449] Falk, J., "Complaint Feedback Loop Operational Recommendations", RFC6449, November 2011. [RFC6590] Falk, J. and M. Kucherawy, "Redaction of Potentially Sensitive Data from Mail Abuse Reports", RFC6590, April 2012. Authors' Addresses J.D. Falk Return Path 100 Mathilda Street, Suite 100 Sunnyvale, CA 94089 USA URI: http://www.returnpath.net/ M. Kucherawy (editor) Cloudmark 128 King St., 2nd Floor San Francisco, CA 94107 US Email: firstname.lastname@example.org Falk & Kucherawy Expires October 27, 2012 [Page 15]