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Versions: 00 01 02 03                                                   
Network Working Group                                      H. Alvestrand
Internet-Draft                                                    Google
Expires: December 28, 2006                                 June 26, 2006

                         UTF-8 Mail: Scenarios

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Copyright Notice

   Copyright (C) The Internet Society (2006).


   This document describes some scenarios in which one can imagine
   internationalized email addresses deployed, and tries to draw some
   conclusions about what's acceptable and what's not for users in those

   One possible set of extensions that can work in these scenarios is
   those described in the UTF8MAIL extension documents.

Requirements Language

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   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  User interface issues  . . . . . . . . . . . . . . . . . .  3
     1.3.  Ignored issues . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Important Scenarios  . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Two i18mail users  . . . . . . . . . . . . . . . . . . . .  4
     2.2.  Three i18mail users  . . . . . . . . . . . . . . . . . . .  5
     2.3.  i18mail mailing list . . . . . . . . . . . . . . . . . . .  5
     2.4.  One i18mail user sends to one ascii user . . . . . . . . .  5
     2.5.  An i18mail user sends to one ascii user and one
           i18mail user . . . . . . . . . . . . . . . . . . . . . . .  6
     2.6.  An i18mail user sends to a mailing list with a mix of
           users  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     2.7.  An i18mail user forwards to an ASCII user  . . . . . . . .  7
   3.  Other scenarios  . . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Two i18mail users, intermediate non-extended MTA . . . . .  7
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  8
   7.  Normative References . . . . . . . . . . . . . . . . . . . . .  8
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . .  9
   Intellectual Property and Copyright Statements . . . . . . . . . . 10

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1.  Introduction

   With the advent of internationalized email addresses [ref], there is
   a very real risk that people using Internet email will have problems
   communicating that they did not have before.  This document tries to
   sketch some of the scenarios, define what "proper" behaviour would be
   in the situations, and describe how this will constrain solutions to
   the "internationalized email" problem.

   Because of the well known phenomenon that short documents get more
   review, the document tries to be as brief as possible, as long as
   that does not sacrifice clarity.

1.1.  Terminology

   Terminology is inherited from the UTF8SMTP framework [I-D.ietf-eai-
   framework] - in particular, the terms "ascii address",
   "internationalized email address" (EAI), "ascii user", "i18mail
   user", "message" and "mailing list" are used with the definitions
   from that document.

   The term "UTF8SMTP" is used to refer to the particular solution
   proposed in that framework, while "i18n mail" refers to any solution
   that could concievably satisfy these scenarios' requirements.

   The pronoun "he" is used to indicate a human of indeterminate sex.

1.2.  User interface issues

   In internationalization, one of the thornier issues has always been
   user interfaces.  In particular in this context, the ability to
   manipulate text strings (email addresses, in this case) in a script
   that the user does not have familiarity with is an issue.

   A main purpose of i18mail is to allow users to avoid doing so when
   corresponding with users in their own language locale when that
   locale normally does not use ASCII - but unless we accept an Internet
   email community of many small fragments, the introduction of "local"
   characters into email addresses will cause users to be exposed to
   addresses that they have trouble recognizing, are unable to enter,
   and in fact may be unable to display; in some cases, even storing the
   addresses is an issue.

   For instance, handling of right-to-left scripts like Arabic in
   environments used to left-to-right scripts like Thai can be a serious

   In order to keep this document short, the following capabilities are

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   o  An i18mail user is able to enter and display directly all
      characters of interest to him in his language locale.

   o  An i18mail user is able to display all valid characters for EAI
      addresses, store them in an address book, and use "reply" without
      damaging the address.

   o  If the i18mail solution requires keeping extra information around
      for an address in some cases, the i18mail user is capable of
      manipulating that information, including storing that information
      in his address book

   One can imagine special circumstances where some of these do not
   represent an optimal solution (for instance, a Thai user may prefer
   to handle the ASCII address of an Arabic correspondent rather than
   his Arabic one), but this is an added complication, and is ignored
   for the moment.

1.3.  Ignored issues

   All the scenarios assume that all parties desire to communicate, that
   spam filters do not eat messages randomly, and that the mail service
   behaves according to specification.  These are not tenable
   assumptions in the real world, but considering them would make this
   document much longer.

2.  Important Scenarios

   In the scenario descriptions below, A, B and C are i18mail users.  X
   (and Y and Z if they need to occur) are ascii users.  L is an i18n-
   aware mailing list; LA (not used yet) is a non-i18n-aware mailing

   Apart from the messages being exchanged, and A knowing the addresses
   of the ones he sends mail to, which are presumed to be made known to
   A through some other method (business cards, web pages, mail from
   other users and directories are some examples), there is no
   communication required between the users.

2.1.  Two i18mail users

   One i18mail user (A) sends a message to another i18mail user (B), and
   desires to use his EAI address.  The recipient replies to the

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   Requirement: The message must arrive at the recipient.  The reply
   must arrive at the sender.  The email addresses visible to the sender
   and recipient must be the EAI addresses.

2.2.  Three i18mail users

   As above, but A sends his message to both B and C. Both reply to all
   the recipients listed in the message.

   Requirement: As above - B and C must get the message, A and C must
   get the reply from B, A and B must get the reply from C. The email
   addresses visible to A, B and C must all be the EAI addresses.

2.3.  i18mail mailing list

   A sends his message to L, a mailing list, which has subscribers B and
   C. Both reply to the mailing list.  The mailing list is i18n aware.

   Requirement: As above - all messages arrive, with EAI addresses
   preserved for all 3 users.

2.4.  One i18mail user sends to one ascii user

   A, an i18mail user, sends to X, an ascii user.  X replies.

   In this scenario, it is a given that A, the sender, has to have some
   facility for handling ASCII; he has to at least be able to display
   and enter an ASCII address.

   Precondition: A has to have an ascii address.

   Requirement: There must be an algorithmic series of steps that A can
   follow in order to get a message to X, and where X's reply gets back
   to A.

   There is no requirement that X sees the EAI address of A, or that the
   address of A that X sees be one that A knows about beforehand; the
   requirement is that the messages get there.  This non-requirement
   applies to all the following cases too.

   Examples of ways this could happen:

   o  Magic happens in the network: A's message gets converted in the
      network to a format acceptable to X. This may require A to include
      extra information with the message to help the conversion process
      - and may be impossible to do for the general case.

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   o  Sender selection: A's i18mail message gets bounced in the network,
      and the reception of the error report causes A to resend the
      message using a format acceptable to X.

   o  Conversion at destination) A's message gets accepted, and X has
      facilities available to convert it into an acceptable form for X,
      including deriving a valid ASCII address for A. This would require
      knowledge of i18n at X's site, but not necessarily in X's user

   This is NOT an exhaustive list, and is NOT part of the requirements
   of the scenarios.  A given protocol for i18mail will in turn impose
   new requirements on the scenarios - for instance, if extra
   information is included with the message, a user interface may need
   to exist to allow the sender to manipulate this information.

2.5.  An i18mail user sends to one ascii user and one i18mail user

   In this scenario, A sends to B and X; both reply.

   Precondition: A and B have to have valid ASCII addresses.

   Requirement: Through some series of steps, A must be able to get a
   message to both B and X; through some series of steps, B and X must
   be able to reply to each other and to A. X must not require
   information outside of what is included in the message to get a
   message to B.

   Possible non-requirements (for discussion):

   o  Maybe the messages to B and X don't need to be exactly the same.

   o  Maybe B doesn't need to see or use A's EAI address when he's
      replying to A and X.

   o  Maybe X doesn't need to see A's address exactly the same on the
      message from A and the reply from B.

2.6.  An i18mail user sends to a mailing list with a mix of users

   In this scenario, A sends to L, and L has B and X as subscribers.  B
   and X reply.

   Requirement: Messages get there.  A will not have to know anything
   about X in order to make the messages go through.

   Notes and non-requirements:

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   o  It may be acceptable for A to have to treat L as if L was an ASCII
      mailing list (LA)

   o  It may be acceptable for B to see A's ASCII address, not his EAI

   o  How one can transition between this and the scenario ofSection 2.3
      is unclear.

2.7.  An i18mail user forwards to an ASCII user

   In this scenario, A sends to B, and B forwards the message as a MIME
   attachment to X.

   Precondition: B has valid ASCII addresses.

   Requirement: The message from B to X should arrive whether or not A's
   address is usable by X.

   Desirable property: If A's address is downgradable, it should be
   usable by X for generating a message.

3.  Other scenarios

   This section collects scenarios that have been discussed, but where
   there is no WG consensus on whether or not they are important enough
   to influence the design of UTF8SMTP.

3.1.  Two i18mail users, intermediate non-extended MTA

   In this scenario, A sends mail to B through an MTA that does not
   support i18mail extensions.

   Requirement: Mail arrives.

   Desirable property: B can see A's I18mail address in his user
   interface, and use that to reply.

   The reason this may not be an important scenario is that due to the
   largely end-to-end nature of SMTP, if the end users have upgraded
   their systems, there should be very little reason to go via a non-
   upgraded MTA.

4.  IANA Considerations

   This document makes no request of IANA.

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   Note to RFC Editor: this section may be removed on publication as an

5.  Security Considerations

   Security issues are deliberately overlooked in order to reduce the
   size of the document.

6.  Acknowledgements

7.  Normative References

              Klensin, J. and Y. Ko, "Overview and Framework for
              Internationalized Email", draft-ietf-eai-framework-00
              (work in progress), May 2006.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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Author's Address

   Harald Tveit Alvestrand

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