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Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1
RFC 7208

Internet Engineering Task Force (IETF)                      S. Kitterman
Request for Comments: 7208                  Kitterman Technical Services
Obsoletes: 4408                                               April 2014
Category: Standards Track
ISSN: 2070-1721

                     Sender Policy Framework (SPF)
           for Authorizing Use of Domains in Email, Version 1

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.

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/rfc7208.

Kitterman                    Standards Track                    [Page 1]
RFC 7208              Sender Policy Framework (SPF)           April 2014

Copyright Notice

   Copyright (c) 2014 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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................5
      1.1. Terminology ................................................5
           1.1.1. Key Words ...........................................5
           1.1.2. Imported Definitions ................................5
           1.1.3. MAIL FROM Definition ................................6
           1.1.4. HELO Definition .....................................6
      1.2. check_host() ...............................................6
   2. Operational Overview ............................................6
      2.1. Publishing Authorization ...................................6
      2.2. Checking Authorization .....................................7
      2.3. The "HELO" Identity ........................................8
      2.4. The "MAIL FROM" Identity ...................................9
      2.5. Location of Checks .........................................9
      2.6. Results of Evaluation ......................................9
           2.6.1. None ...............................................10
           2.6.2. Neutral ............................................10
           2.6.3. Pass ...............................................10
           2.6.4. Fail ...............................................10

Kitterman                    Standards Track                    [Page 2]
RFC 7208              Sender Policy Framework (SPF)           April 2014

           2.6.5. Softfail ...........................................10
           2.6.6. Temperror ..........................................10
           2.6.7. Permerror ..........................................10

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