Overview and Framework for Internationalized Email
RFC 6530

Internet Engineering Task Force (IETF)                        J. Klensin
Request for Comments: 6530                                         Y. Ko
Obsoletes: 4952, 5504, 5825                                February 2012
Category: Standards Track
ISSN: 2070-1721

           Overview and Framework for Internationalized Email

Abstract

   Full use of electronic mail throughout the world requires that
   (subject to other constraints) people be able to use close variations
   on their own names (written correctly in their own languages and
   scripts) as mailbox names in email addresses.  This document
   introduces a series of specifications that define mechanisms and
   protocol extensions needed to fully support internationalized email
   addresses.  These changes include an SMTP extension and extension of
   email header syntax to accommodate UTF-8 data.  The document set also
   includes discussion of key assumptions and issues in deploying fully
   internationalized email.  This document is a replacement for RFC
   4952; it reflects additional issues identified since that document
   was published.

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/rfc6530.

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
   carefully, as they describe your rights and restrictions with respect

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RFC 6530            Internationalized Email Framework      February 2012

   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
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   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.

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RFC 6530            Internationalized Email Framework      February 2012

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Role of This Specification . . . . . . . . . . . . . . . . . .  4
   3.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Mail User and Mail Transfer Agents . . . . . . . . . . . .  6
     4.2.  Address Character Sets . . . . . . . . . . . . . . . . . .  7
     4.3.  User Types . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.4.  Messages . . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.5.  Mailing Lists  . . . . . . . . . . . . . . . . . . . . . .  8
     4.6.  Conventional Message and Internationalized Message . . . .  8
     4.7.  Undeliverable Messages, Notification, and Delivery
           Receipts . . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Overview of the Approach and Document Plan . . . . . . . . . .  9
   6.  Review of Experimental Results . . . . . . . . . . . . . . . .  9
   7.  Overview of Protocol Extensions and Changes  . . . . . . . . . 10
     7.1.  SMTP Extension for Internationalized Email Address . . . . 10
     7.2.  Transmission of Email Header Fields in UTF-8 Encoding  . . 11
     7.3.  SMTP Service Extension for DSNs  . . . . . . . . . . . . . 12
   8.  Downgrading before and after SMTP Transactions . . . . . . . . 12