EAI: Simplified POP/IMAP downgrading
draft-ietf-eai-simpledowngrade-02

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Last updated 2012-03-26
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Network Working Group                                   Arnt Gulbrandsen
Internet-Draft                                                March 2012
Intended Status: Proposed Standard
Updates: 3501

                  EAI: Simplified POP/IMAP downgrading
                 draft-ietf-eai-simpledowngrade-02.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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Gulbrandsen              Expires September 2012                 [Page 1]
Internet-draft                                                March 2012

Abstract

   This document specifies a method for IMAP and POP servers to serve
   internationalized messages to conventional clients. The specification
   is simple, easy to implement and provides only rudimentary results.

1. Overview

   It may happen that a conventional IMAP or POP client opens a mailbox
   containing internationalized messages, or even attempt to read
   internationalized messages, for instance when a user has both
   internationalized and conventional MUAs.

   While the server can hide the existence of such messages entirely,
   doing that can be both tricky to implement and not very friendly to
   the user.

   This document specifies a way to present such messages to the client.
   It values simplicity of implementation over fidelity of
   representation, on the theory that anyone who wants accuracy should
   use an internationalized client, and that client implementers' time
   should be reserved for implementing [RFC6531], [RFC5738] and/or
   [RFC5721].

   The server is assumed to be internationalized internally. When it
   needs to present an internationalized message to a conventional
   client, it synthesizes a conventional message containing most of the
   information and presents that (the "synthetic message").

2. Information preserved and lost

   The synthetic message is intended to convey the most important
   information to the user. Where information is lost, the user should
   see the message as incomplete rather than modified.

   The synthetic message is not intended to convey any information to
   the MUA. Nothing parsable is added, not even a marker to say "this
   message has been downgraded".

   Upper case in examples represents non-ASCII. example.com is a plain
   domain, EXAMPLE.com represents a non-ASCII .com domain.

Gulbrandsen              Expires September 2012                 [Page 2]
Internet-draft                                                March 2012

2.1 Email addresses

   Each internationalized email address in the header fields listed
   below is replaced with an invalid email address whose display-name
   tells the user what happened.

   The format of the display-name is explicitly unspecified. Anything
   which tells the user what happened is good. Anything which produces
   an email address which might belong to someone else is bad.

   Given an internationalized address "Fred <fred@EXAMPLE.com>", an
   implementation may choose to render it e.g. as these examples:

      "fred@EXAMPLE.com" <invalid@eai.invalid>
      Fred <invalid@eai.invalid>
      eai-address:;
      fred:;

   (The .invalid top-level domain is reserved by [RFC2606], therefore
   the first two examples are syntactically valid, but will never belong
   to anyone. Note that the display-name often will need [RFC2047]
   encoding.)

   The affected header fields are Bcc, Cc, From, Reply-To, Resent-Bcc,
   Resent-Cc, Resent-From, Resent-Sender, Resent-To, Return-Path, Sender
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