Sieve: Internationalized Email

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Network Working Group                                           S. Bosch
Internet-Draft                                                Dovecot Oy
Intended status: Standards Track                           21 March 2020
Expires: 22 September 2020

                     Sieve: Internationalized Email


   This document defines an extension to the Sieve language called "eai"
   which adds full support for internationalized email.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 22 September 2020.

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Table of Contents

   1.  Introduction
   2.  Conventions Used in This Document
   3.  Headers
   4.  Addresses
   5.  Modified commands
       5.1.  Test address
       5.2.  Test header
       5.3.  Action redirect
   6.  Modified extensions
       6.1.  Body Extension
       6.2.  Convert Extension
       6.3.  Editheader Extension
       6.4.  Envelope Extension
       6.5.  Enotify Extension
       6.6.  Reject and Extended Reject Extensions
       6.7.  Mime Extension
       6.8.  Replace Extension
       6.9.  Enclose Extension
       6.10.  Other Extensions?
   7.  Downgrading
   8.  Mailing lists
   9.  Examples
   10.  Acknowledgements
   11.  IANA Considerations
   12.  Security Considerations
   13.  References
       13.1.  Normative References
       13.2.  Informative References
   Author's Address

1.  Introduction

   Many parts of the Sieve mail filtering language [SIEVE] such as
   strings and comments are already designed primarily for use with the
   UTF-8 encoding [UTF-8] , thereby supporting all the international
   characters specified by the Unicode standard.  Also, Sieve can
   already work with message header fields that contain UTF-8
   characters, provided these are encoded using MIME encoded-word
   [MIME3].  However, the Sieve language was conceived before the
   Framework for Internationalized Email [RFC6530] was finished, which
   means that filtered email messages are still restricted to the
   conventional Internet Message Format [IMAIL], which mainly means that
   only the conventional US-ASCII email addresses can be used [SMTP].
   This poses problems for using the Sieve language in a mail system
   where internationalized email is to be supported.

   This document defines an extension to the Sieve language called "eai"
   which adds full support for internationalized email.

   [FIXME: Any ideas for a better name for the extension?]

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [KEYWORDS] [KEYWORDS-UPD] when, and only when, they appear in
   all capitals, as shown here.

3.  Headers

   The "eai" extension presented in this document does not alter the
   handling of conventional Internet messages [IMAIL], which have
   content type "message/rfc822".  For such conventional messages, it
   expects UTF-8 characters in header field values to be encoded using
   MIME encoded-words [MIME3].  In contrast, when the filtered message
   (or message part) has content type "message/global" [RFC6532], the
   header field value can contain UTF-8 characters directly and MIME
   encoded-words SHOULD NOT be interpreted.

   Note that internationalized email header names are still restricted
   to ASCII characters only [RFC6532], which means that the Sieve tests
   in which header fields are evaluated will never match when the
   provided header name contains UTF-8 characters.

4.  Addresses

   Section of [SIEVE] defines a constrained version of the US-
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