SPF
SPF (Sender Policy Framework)
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SPF RFCs (21)
RFC 9991: Domain-Based Message Authentication, Reporting, and Conformance (DMARC) Failure Reporting
Proposed Standard- S. Jones
- A. Vesely
- May 2026
- IETF publication
- Applications and Real-Time Area
Abstract
Domain-based Message Authentication, Reporting, and Conformance (DMARC) is a mechanism by which a Domain Owner can request feedback about email messages using their domain in the From: address field. This document describes "failure reports", or "failed message reports", which provide details about individual messages that failed to authenticate according to the DMARC mechanism.
This document updates RFC 6591 and obsoletes RFC 7489.
Abstract
Domain-based Message Authentication, Reporting, and Conformance (DMARC) is a mechanism by which a Domain Owner can request feedback about email messages using their domain in the From: address field. This document describes "failure reports", or "failed message reports", which provide details about individual messages that failed to authenticate according to the DMARC mechanism.
This document updates RFC 6591 and obsoletes RFC 7489.
RFC 9057: Email Author Header Field
Experimental- D. Crocker
- June 2021
- Independent Stream publication
Abstract
Internet mail defines the From: header field to indicate the author of the message's content and the Sender: field to indicate who initially handled the message on the author's behalf. The Sender: field is optional if it has the same information as the From: field. This was not a problem until development of stringent protections on use of the From: field. It has prompted Mediators, such as mailing lists, to modify the From: field to circumvent mail rejection caused by those protections. In effect, the From: field has become dominated by its role as a handling identifier.
The current specification augments the altered use of the From: field by specifying the Author: field, which ensures identification of the original author of the message and is not subject to modification by Mediators. This document is published as an Experimental RFC to assess community interest, functional efficacy, and technical adequacy.
Abstract
Internet mail defines the From: header field to indicate the author of the message's content and the Sender: field to indicate who initially handled the message on the author's behalf. The Sender: field is optional if it has the same information as the From: field. This was not a problem until development of stringent protections on use of the From: field. It has prompted Mediators, such as mailing lists, to modify the From: field to circumvent mail rejection caused by those protections. In effect, the From: field has become dominated by its role as a handling identifier.
The current specification augments the altered use of the From: field by specifying the Author: field, which ensures identification of the original author of the message and is not subject to modification by Mediators. This document is published as an Experimental RFC to assess community interest, functional efficacy, and technical adequacy.
RFC 8601: Message Header Field for Indicating Message Authentication Status
Proposed Standard- M. Kucherawy
- May 2019
- IETF publication
- Applications and Real-Time Area
Abstract
This document specifies a message header field called "Authentication-Results" for use with electronic mail messages to indicate the results of message authentication efforts. Any receiver-side software, such as mail filters or Mail User Agents (MUAs), can use this header field to relay that information in a convenient and meaningful way to users or to make sorting and filtering decisions.
This document obsoletes RFC 7601.
Abstract
This document specifies a message header field called "Authentication-Results" for use with electronic mail messages to indicate the results of message authentication efforts. Any receiver-side software, such as mail filters or Mail User Agents (MUAs), can use this header field to relay that information in a convenient and meaningful way to users or to make sorting and filtering decisions.
This document obsoletes RFC 7601.
RFC 8405: Shortest Path First (SPF) Back-Off Delay Algorithm for Link-State IGPs
Proposed Standard- B. Decraene
- S. Litkowski
- H. Gredler
- A. Lindem
- P. Francois
- C. Bowers
- June 2018
- IETF publication
- Routing Area
Abstract
This document defines a standard algorithm to temporarily postpone or "back off" link-state IGP Shortest Path First (SPF) computations. This reduces the computational load and churn on IGP nodes when multiple temporally close network events trigger multiple SPF computations.
Having one standard algorithm improves interoperability by reducing the probability and/or duration of transient forwarding loops during the IGP convergence when the IGP reacts to multiple temporally close IGP events.
Abstract
This document defines a standard algorithm to temporarily postpone or "back off" link-state IGP Shortest Path First (SPF) computations. This reduces the computational load and churn on IGP nodes when multiple temporally close network events trigger multiple SPF computations.
Having one standard algorithm improves interoperability by reducing the probability and/or duration of transient forwarding loops during the IGP convergence when the IGP reacts to multiple temporally close IGP events.
RFC 7960: Interoperability Issues between Domain-based Message Authentication, Reporting, and Conformance (DMARC) and Indirect Email Flows
Informational- F. Martin
- E. Lear
- T. Draegen
- E. Zwicky
- K. Andersen
- September 2016
- IETF publication
- Applications and Real-Time Area
Abstract
Domain-based Message Authentication, Reporting, and Conformance (DMARC) introduces a mechanism for expressing domain-level policies and preferences for email message validation, disposition, and reporting. However, the DMARC mechanism enables potentially disruptive interoperability issues when messages do not flow directly from the author's administrative domain to the final Recipients. Collectively, these email flows are referred to as "indirect email flows". This document describes these interoperability issues and presents possible methods for addressing them.
Abstract
Domain-based Message Authentication, Reporting, and Conformance (DMARC) introduces a mechanism for expressing domain-level policies and preferences for email message validation, disposition, and reporting. However, the DMARC mechanism enables potentially disruptive interoperability issues when messages do not flow directly from the author's administrative domain to the final Recipients. Collectively, these email flows are referred to as "indirect email flows". This document describes these interoperability issues and presents possible methods for addressing them.
RFC 7601: Message Header Field for Indicating Message Authentication Status
Proposed Standard- M. Kucherawy
- August 2015
- IETF publication
- Applications and Real-Time Area
Abstract
This document specifies a message header field called Authentication- Results for use with electronic mail messages to indicate the results of message authentication efforts. Any receiver-side software, such as mail filters or Mail User Agents (MUAs), can use this header field to relay that information in a convenient and meaningful way to users or to make sorting and filtering decisions.
Obsoleted by RFC 8601
Abstract
This document specifies a message header field called Authentication- Results for use with electronic mail messages to indicate the results of message authentication efforts. Any receiver-side software, such as mail filters or Mail User Agents (MUAs), can use this header field to relay that information in a convenient and meaningful way to users or to make sorting and filtering decisions.
RFC 7489: Domain-based Message Authentication, Reporting, and Conformance (DMARC)
Informational- M. Kucherawy
- E. Zwicky
- March 2015
- Independent Stream publication
Abstract
Domain-based Message Authentication, Reporting, and Conformance (DMARC) is a scalable mechanism by which a mail-originating organization can express domain-level policies and preferences for message validation, disposition, and reporting, that a mail-receiving organization can use to improve mail handling.
Originators of Internet Mail need to be able to associate reliable and authenticated domain identifiers with messages, communicate policies about messages that use those identifiers, and report about mail using those identifiers. These abilities have several benefits: Receivers can provide feedback to Domain Owners about the use of their domains; this feedback can provide valuable insight about the management of internal operations and the presence of external domain name abuse.
DMARC does not produce or encourage elevated delivery privilege of authenticated email. DMARC is a mechanism for policy distribution that enables increasingly strict handling of messages that fail authentication checks, ranging from no action, through altered delivery, up to message rejection.
Abstract
Domain-based Message Authentication, Reporting, and Conformance (DMARC) is a scalable mechanism by which a mail-originating organization can express domain-level policies and preferences for message validation, disposition, and reporting, that a mail-receiving organization can use to improve mail handling.
Originators of Internet Mail need to be able to associate reliable and authenticated domain identifiers with messages, communicate policies about messages that use those identifiers, and report about mail using those identifiers. These abilities have several benefits: Receivers can provide feedback to Domain Owners about the use of their domains; this feedback can provide valuable insight about the management of internal operations and the presence of external domain name abuse.
DMARC does not produce or encourage elevated delivery privilege of authenticated email. DMARC is a mechanism for policy distribution that enables increasingly strict handling of messages that fail authentication checks, ranging from no action, through altered delivery, up to message rejection.
RFC 7208: Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1
Proposed Standard- S. Kitterman
- April 2014
- IETF publication
- Applications Area
Abstract
Email on the Internet can be forged in a number of ways. In particular, existing protocols place no restriction on what a sending host can use as the "MAIL FROM" of a message or the domain given on the SMTP HELO/EHLO commands. This document describes version 1 of the Sender Policy Framework (SPF) protocol, whereby ADministrative Management Domains (ADMDs) can explicitly authorize the hosts that are allowed to use their domain names, and a receiving host can check such authorization.
This document obsoletes RFC 4408.
Abstract
Email on the Internet can be forged in a number of ways. In particular, existing protocols place no restriction on what a sending host can use as the "MAIL FROM" of a message or the domain given on the SMTP HELO/EHLO commands. This document describes version 1 of the Sender Policy Framework (SPF) protocol, whereby ADministrative Management Domains (ADMDs) can explicitly authorize the hosts that are allowed to use their domain names, and a receiving host can check such authorization.
This document obsoletes RFC 4408.
RFC 7070: An Architecture for Reputation Reporting
Proposed Standard- N. Borenstein
- M. Kucherawy
- November 2013
- IETF publication
- Applications Area
Abstract
This document describes a general architecture for a reputation-based service, allowing one to request reputation-related data over the Internet, where "reputation" refers to predictions or expectations about an entity or an identifier such as a domain name. The document roughly follows the recommendations of RFC 4101 for describing a protocol model.
Abstract
This document describes a general architecture for a reputation-based service, allowing one to request reputation-related data over the Internet, where "reputation" refers to predictions or expectations about an entity or an identifier such as a domain name. The document roughly follows the recommendations of RFC 4101 for describing a protocol model.
RFC 7071: A Media Type for Reputation Interchange
Proposed Standard- N. Borenstein
- M. Kucherawy
- November 2013
- IETF publication
- Applications Area
Abstract
This document defines the format of reputation response data ("reputons"), the media type for packaging it, and definition of a registry for the names of reputation applications and response sets.
Abstract
This document defines the format of reputation response data ("reputons"), the media type for packaging it, and definition of a registry for the names of reputation applications and response sets.
RFC 7072: A Reputation Query Protocol
Proposed Standard- N. Borenstein
- M. Kucherawy
- November 2013
- IETF publication
- Applications Area
Abstract
This document defines a mechanism to conduct queries for reputation information over the HyperText Transfer Protocol (HTTP) using JavaScript Object Notation (JSON) as the payload meta-format.
Abstract
This document defines a mechanism to conduct queries for reputation information over the HyperText Transfer Protocol (HTTP) using JavaScript Object Notation (JSON) as the payload meta-format.
RFC 7073: A Reputation Response Set for Email Identifiers
Proposed Standard- N. Borenstein
- M. Kucherawy
- November 2013
- IETF publication
- Applications Area
Abstract
This document defines a response set for describing assertions a reputation service provider can make about email identifiers, for use in generating reputons.
Abstract
This document defines a response set for describing assertions a reputation service provider can make about email identifiers, for use in generating reputons.
RFC 7001: Message Header Field for Indicating Message Authentication Status
Proposed Standard- M. Kucherawy
- September 2013
- IETF publication
- Applications and Real-Time Area
Abstract
This document specifies a message header field called Authentication- Results for use with electronic mail messages to indicate the results of message authentication efforts. Any receiver-side software, such as mail filters or Mail User Agents (MUAs), can use this header field to relay that information in a convenient and meaningful way to users or to make sorting and filtering decisions.
Obsoleted by RFC 7601
Abstract
This document specifies a message header field called Authentication- Results for use with electronic mail messages to indicate the results of message authentication efforts. Any receiver-side software, such as mail filters or Mail User Agents (MUAs), can use this header field to relay that information in a convenient and meaningful way to users or to make sorting and filtering decisions.
RFC 6686: Resolution of the Sender Policy Framework (SPF) and Sender ID Experiments
Informational- M. Kucherawy
- July 2012
- IETF publication
- Applications Area
Abstract
In 2006, the IETF published a suite of protocol documents comprising the Sender Policy Framework (SPF) and Sender ID: two proposed email authentication protocols. Both of these protocols enable one to publish, via the Domain Name System, a policy declaring which mail servers were authorized to send email on behalf of the domain name being queried. There was concern that the two would conflict in some significant operational situations, interfering with message delivery.
The IESG required all of these documents (RFC 4405, RFC 4406, RFC 4407, and RFC 4408) to be published as Experimental RFCs and requested that the community observe deployment and operation of the protocols over a period of two years from the date of publication to determine a reasonable path forward.
After six years, sufficient experience and evidence have been collected that the experiments thus created can be considered concluded. This document presents those findings. This document is not an Internet Standards Track specification; it is published for informational purposes.
Abstract
In 2006, the IETF published a suite of protocol documents comprising the Sender Policy Framework (SPF) and Sender ID: two proposed email authentication protocols. Both of these protocols enable one to publish, via the Domain Name System, a policy declaring which mail servers were authorized to send email on behalf of the domain name being queried. There was concern that the two would conflict in some significant operational situations, interfering with message delivery.
The IESG required all of these documents (RFC 4405, RFC 4406, RFC 4407, and RFC 4408) to be published as Experimental RFCs and requested that the community observe deployment and operation of the protocols over a period of two years from the date of publication to determine a reasonable path forward.
After six years, sufficient experience and evidence have been collected that the experiments thus created can be considered concluded. This document presents those findings. This document is not an Internet Standards Track specification; it is published for informational purposes.
RFC 6652: Sender Policy Framework (SPF) Authentication Failure Reporting Using the Abuse Reporting Format
Proposed Standard- S. Kitterman
- June 2012
- IETF publication
- Applications Area
Abstract
This memo presents extensions to the Abuse Reporting Format (ARF) and Sender Policy Framework (SPF) specifications to allow for detailed reporting of message authentication failures in an on-demand fashion.
This memo updates RFC 4408 by providing an IANA registry for SPF modifiers. [STANDARDS-TRACK]
Abstract
This memo presents extensions to the Abuse Reporting Format (ARF) and Sender Policy Framework (SPF) specifications to allow for detailed reporting of message authentication failures in an on-demand fashion.
This memo updates RFC 4408 by providing an IANA registry for SPF modifiers. [STANDARDS-TRACK]
RFC 6591: Authentication Failure Reporting Using the Abuse Reporting Format
Proposed Standard- H. Fontana
- April 2012
- IETF publication
- Applications Area
Abstract
This memo registers an extension report type for the Abuse Reporting Format (ARF), affecting multiple registries, for use in generating receipt-time reports about messages that fail one or more email message authentication checks. [STANDARDS-TRACK]
Abstract
This memo registers an extension report type for the Abuse Reporting Format (ARF), affecting multiple registries, for use in generating receipt-time reports about messages that fail one or more email message authentication checks. [STANDARDS-TRACK]
RFC 6577: Authentication-Results Registration Update for Sender Policy Framework (SPF) Results
Proposed Standard- M. Kucherawy
- March 2012
- IETF publication
Abstract
This memo updates the registry of authentication method results in Authentication-Results: message header fields, correcting a discontinuity between the original registry creation and the Sender Policy Framework (SPF) specification. [STANDARDS-TRACK]
Obsoleted by RFC 7001
Abstract
This memo updates the registry of authentication method results in Authentication-Results: message header fields, correcting a discontinuity between the original registry creation and the Sender Policy Framework (SPF) specification. [STANDARDS-TRACK]
RFC 6008: Authentication-Results Registration for Differentiating among Cryptographic Results
Proposed Standard- M. Kucherawy
- September 2010
- IETF publication
Abstract
This memo updates the registry of properties in Authentication- Results: message header fields to allow a multiple-result report to distinguish among one or more cryptographic signatures on a message, thus associating specific results with the signatures they represent. [STANDARDS-TRACK]
Abstract
This memo updates the registry of properties in Authentication- Results: message header fields to allow a multiple-result report to distinguish among one or more cryptographic signatures on a message, thus associating specific results with the signatures they represent. [STANDARDS-TRACK]
RFC 4408: Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1
Experimental- M. Wong
- W. Schlitt
- April 2006
- IETF publication
Abstract
E-mail on the Internet can be forged in a number of ways. In particular, existing protocols place no restriction on what a sending host can use as the reverse-path of a message or the domain given on the SMTP HELO/EHLO commands. This document describes version 1 of the ender Policy Framework (SPF) protocol, whereby a domain may explicitly authorize the hosts that are allowed to use its domain name, and a receiving host may check such authorization. This memo defines an Experimental Protocol for the Internet community.
Obsoleted by RFC 7208
Abstract
E-mail on the Internet can be forged in a number of ways. In particular, existing protocols place no restriction on what a sending host can use as the reverse-path of a message or the domain given on the SMTP HELO/EHLO commands. This document describes version 1 of the ender Policy Framework (SPF) protocol, whereby a domain may explicitly authorize the hosts that are allowed to use its domain name, and a receiving host may check such authorization. This memo defines an Experimental Protocol for the Internet community.
RFC 3906: Calculating Interior Gateway Protocol (IGP) Routes Over Traffic Engineering Tunnels
Informational- N. Shen
- H. Smit
- October 2004
- IETF publication
- Routing Area
Abstract
This document describes how conventional hop-by-hop link-state routing protocols interact with new Traffic Engineering capabilities to create Interior Gateway Protocol (IGP) shortcuts. In particular, this document describes how Dijkstra's Shortest Path First (SPF) algorithm can be adapted so that link-state IGPs will calculate IP routes to forward traffic over tunnels that are set up by Traffic Engineering. This memo provides information for the Internet community.
Abstract
This document describes how conventional hop-by-hop link-state routing protocols interact with new Traffic Engineering capabilities to create Interior Gateway Protocol (IGP) shortcuts. In particular, this document describes how Dijkstra's Shortest Path First (SPF) algorithm can be adapted so that link-state IGPs will calculate IP routes to forward traffic over tunnels that are set up by Traffic Engineering. This memo provides information for the Internet community.
RFC 1074: NSFNET backbone SPF based Interior Gateway Protocol
Unknown- J. Rekhter
- October 1988
- Legacy publication
Abstract
This RFC is an implementation description of the standard ANSI IS-IS and ISO ES-IS routing protocols within the NSFNET backbone network.
Abstract
This RFC is an implementation description of the standard ANSI IS-IS and ISO ES-IS routing protocols within the NSFNET backbone network.
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