Email Address Internationalization J. Klensin (EAI) Internet-Draft Y. Ko Expires: December 25, 2006 MOCOCO, Inc. June 23, 2006 Overview and Framework for Internationalized Email draft-ietf-eai-framework-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 25, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract Full use of electronic mail throughout the world requires that people be able to use their own names, written correctly in their own languages and scripts, as mailbox names in email addresses. This document introduces a series of specifications and operational suggestions 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 Klensin & Ko Expires December 25, 2006 [Page 1]
Internet-Draft EAI Framework June 2006 accommodate UTF-8 data. The document set also will include discussion of key assumptions and issues in deploying fully internationalized email. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Role of This Specification . . . . . . . . . . . . . . . . 3 1.2. Problem statement . . . . . . . . . . . . . . . . . . . . 3 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 2. Overview of the Approach . . . . . . . . . . . . . . . . . . . 6 3. Document Roadmap . . . . . . . . . . . . . . . . . . . . . . . 6 4. Overview of Protocol Extensions and Changes . . . . . . . . . 7 4.1. SMTP Extension for Internationalized eMail Address . . . . 7 4.2. Transmission of Email Header in UTF-8 Encoding . . . . . . 8 4.3. Downgrading Mechanism for Backward Compatibility . . . . . 8 5. Downgrading Before and After SMTP Transactions . . . . . . . . 9 5.1. Downgrading Before or During Message Submission . . . . . 9 5.2. Downgrading or Other Processing After Final SMTP Delivery . . . . . . . . . . . . . . . . . . . . . . . . . 10 6. Advice to Designers and Operators of Mail-receiving Systems . 10 7. Internationalization Considerations . . . . . . . . . . . . . 11 8. Additional Issues . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Impact on IRIs . . . . . . . . . . . . . . . . . . . . . . 11 8.2. POP and IMAP . . . . . . . . . . . . . . . . . . . . . . . 11 9. Experimental Targets . . . . . . . . . . . . . . . . . . . . . 12 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 11. Security Considerations . . . . . . . . . . . . . . . . . . . 12 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 13. Change History . . . . . . . . . . . . . . . . . . . . . . . . 13 13.1. draft-klensin-ima-framework: Version 00 . . . . . . . . . 14 13.2. draft-klensin-ima-framework: Version 01 . . . . . . . . . 14 13.3. draft-ietf-eai-framework: Version 00 . . . . . . . . . . . 14 13.4. draft-ietf-eai-framework: Version 01 . . . . . . . . . . . 14 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 14.1. Normative References . . . . . . . . . . . . . . . . . . . 15 14.2. Informative References . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . . . . 19 Klensin & Ko Expires December 25, 2006 [Page 2]
Internet-Draft EAI Framework June 2006 1. Introduction [[anchor1: NOTE IN DRAFT: The next version of this document (-01) will include references that are updated as appropriate to utilize the new names of documents and a list of documents that are harmonized with the WG Charter. This version is transitional and those reading it are asked to be tolerant of the transition.]] In order to use internationalized email addresses, we need to internationalize both domain part and local part of email address. The domain part of email addresses is already internationalized [RFC3490], while the local part is not. Without these extensions, the mailbox name is restricted to a subset of 7-bit ASCII in [RFC2821]. Though MIME enables the transport of non-ASCII data, it does not provide a mechanism for internationalized email address. [RFC2047] defines an encoding mechanism for some specific message header fields to accommodate non-ASCII data. However, it does not address the issue of email addresses that include non-ASCII characters. Without the extensions defined here, or some equivalent set, the only way to incorporate non-ASCII characters in email addresses is to use RFC2047 coding to embed them in what RFC 2822 [RFC2822] calls the "display name" (known as a "name phrase" or by other terms elsewhere) of the relevant headers. Of course, that type of coding is invisible in the message envelope and would not be considered by many to be part of the address at all. 1.1. Role of This Specification This document presents the overview and framework for an approach to the next stage of email internationalization. This new stage requires not only internationalization of addresses and headers, but also associated transport and delivery models. The history of developments and design ideas leading to this specification is described in [I18Nemail-history]. This document describes how the various elements of email internationalization fit together and provides a roadmap for navigating the various documents involved. 1.2. Problem statement [[anchor2: Note in draft: this section needs very significant reworking for both content and presentation. Changed with -01c, but may still not be good enough]] Though domain names are already internationalized, the internationalized forms are far from general adoption by ordinary users. One of the reasons for this is that we do not yet have fully Klensin & Ko Expires December 25, 2006 [Page 3]
Internet-Draft EAI Framework June 2006 internationalized naming schemes. Domain names are just one of the various names and identifiers that are required to be internationalized. Email addresses are a particularly important example of where internationalization of domain names alone is not sufficient. Unless email addresses are presented to the user in familiar characters and formats, the user's perception will not be of internationalization and behavior that is culturally friendly. One thing most of us have almost certainly learned from the experience with email usage is that users strongly prefer email addresses that closely resemble names or initials to those involving meaningless strings of letters or numbers. If the names or initials of the names in the email address can be expressed in the native languages and writing systems of the users, the Internet will be perceived as more natural by those whose native language is not written in a subset of a Roman-derived script (this is the same collection of characters known as "Latin" in Unicode Consortium and ISO/IEC JTC1 publications. In much of the linguistic literature, the term "Latin Script" is used exclusively for the characters used to write the Latin language at the time of the Roman Republic, so its use for all characters constructed from that base has been a source of confusion.). Internationalization of email addresses is not merely a matter of changing the SMTP envelope, or of modifying the From, To, and Cc headers, or of permitting upgraded mail user agents (MUAs) to decode a special coding and display local characters. To be perceived as usable by end users, the addresses must be internationalized, and handled consistently, in all of the contexts in which they occur. That requirement has far-reaching implications: collections of patches and workarounds are not adequate. Even if they were adequate, that approach risks an assortment of implementations with different sets of patches and workarounds having been applied with consequent user confusion about what is actually be run and supported. Instead, we need to build a fully internationalized email environment, focusing on permitting efficient communication among those who share a language or other community (see [I18Nemail- constraints] for an extended discussion of this optimization). That, in turn, implies changes to the mail header environment to permit the full range of Unicode characters where that makes sense, an SMTP extension to permit UTF-8 [RFC3629] mail addressing and delivery of those extended headers, and (finally) a requirement for support of the 8BITMIME option so that all of this can be transported through the mail system without having to overcome the limitation that headers do not have content-transfer-encodings. Klensin & Ko Expires December 25, 2006 [Page 4]
Internet-Draft EAI Framework June 2006 1.3. Terminology This document assumes a reasonable understanding of the protocols and terminology of the core email standards as documented in [RFC2821] and [RFC2822]. Much of the description in this document depends on the abstractions of "Mail Transfer Agent" ("MTA") and "Mail User Agent" ("MUA"). However, it is important to understand that those terms and the underlying concepts postdate the design of the Internet's email architecture and the "protocols on the wire" principle. That email architecture, as it has evolved, and the "wire" principle have prevented any strong and standardized distinctions about how MTAs and MUAs interact on a given origin or destination host (or even whether they are separate). In this document, an address is "all-ASCII", or just an "ASCII address", if every character in the address is in the ASCII character repertoire [ASCII]; an address is "non-ASCII", or an "i18mail address", if any character is not in the ASCII character repertoire. Such addresses may be restricted in other ways, but those restrictions are not relevant here. The term "all-ASCII" is also applied to other protocol elements when the distinction is important, with "non-ASCII" or "internationalized" as its opposite. The umbrella term to describe the email address internationalization specified by this document and its companion documents is "UTF8SMTP". [[anchor4: This term will be verified by further WG discussions.]] For example, an address permitted by this specification is referred as a "UTF8SMTP (compliant) address". [[anchor5: Terminology from "scenarios" follows]] An "ASCII user" (i) uses only email addresses that contain ASCII characters only, and (ii) cannot generate recipient addresses that contain non-ASCII characters. An "i18mail user" has one or more i18mail addresses. He may have ascii addresses too; if he has more than one email address, he has some method to choose which address to use on outgoing email. Note that under this definition, it is not possible to tell from the address that an email sender or recipient is an i18mail user. [[anchor6: This may need to be changed, consist with text in "scenarios"]] A "message" is sent from one user (sender) using a particular email address to one or more other recipient email addresses (often referred to just as "users" or "recipient users"). Klensin & Ko Expires December 25, 2006 [Page 5]
Internet-Draft EAI Framework June 2006 A "mailing list" is a mechanism whereby a message may be distributed to multiple recipients by sending to one recipient address. An agent (typically not a human being) at that single address then causes the message to be redistributed to the target recipients. [[anchor7: The original language here ("...an user can cause...") is wrong since it implies user intention. And "not under control of" is also usually, but not always, true. While those conditions will often be the case, a user generally don't know if a recipient address is a list or not. VRFY and EXPN were designed to let would-be senders find out, but they are operationally moribund. We should be sure that, if 2821 has a definition for "mailing list", it is consistent (and, if it doesn't, get a consistent definition intov 2821bis).]] The pronoun "he" is used to indicate a human of indeterminate gender. The key words "MUST", "SHALL", "REQUIRED", "SHOULD", "RECOMMENDED", and "MAY" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2. Overview of the Approach This set of specifications changes both SMTP and the format of email headers to permit non-ASCII characters to be represented directly. Each important component of the work is described in a separate document. The document set, whose members are described in the next section, also contains informational documents whose purpose is to provide operational and implementation suggestions and guidance for the protocols. 3. Document Roadmap In addition to this document, the following documents make up this specification and provide advice and context for it. o SMTP extensions. This document provides an SMTP extension for internationalized addresses, as provided for in RFC 2821 [I18Nemail-SMTPext]. o Email headers in UTF-8. This document essentially updates RFC 2822 to permit some information in email headers to be expressed directly by Unicode characters encoded in UTF-8 when the SMTP extension is used [I18Nemail-UTF8]. o In-transit downgrading from internationalized addressing with the SMTP extension and UTF-8 headers to traditional email formats and characters [I18Nemail-downgrade]. Downgrading either at the point of message origination or after the mail has successfully been received by a final delivery SMTP server (sometimes called an Klensin & Ko Expires December 25, 2006 [Page 6]
Internet-Draft EAI Framework June 2006 "MDA") involve different constraints and possibilities; see Section 4.3 and Section 5, below. o Extensions to the IMAP protocol to support internationalized headers [I18Nemail-imap]. o Parallel extensions to the POP protocol [I18Nemail-pop]. o Scenarios for the use of these protocols [I18Nemail-scenarios]. o Special considerations for mailing lists and similar distributions during the transition to internationalized email [I18Nemail- Exploder]. o Design decisions, history, and alternative models for internationalized Internet email [I18Nemail-history]. This document is not expected to be a WG product 4. Overview of Protocol Extensions and Changes 4.1. SMTP Extension for Internationalized eMail Address An SMTP extension, "Email18N" [[anchor11: Extension name should be corrected when we make a final decision and synchronized with the "I18Nemail-SMTPext" document]] is specified that o Permits the use of UTF-8 strings in email addresses, both local parts and domain names o Permits the selective use of UTF-8 strings in email headers (see the next subsection) o Requires that the server advertise the 8BITMIME extension [RFC1652] and that the client support 8-bit transmission so that header information can be transmitted without using a special content-transfer-encoding. o Provides information to support downgrading mechanisms. Some general principles apply to this work. 1. Whatever encoding is used should apply to the whole address and be directly compatible with software used at the user interface. 2. An SMTP relay must * Either recognize the format explicitly, agreeing to do so via an ESMTP option, * Select and use an ASCII-only address, or * Bounce the message so that the sender can make another plan. If the message cannot be forwarded because the next-hop system cannot accept the extension and insufficient information is available to reliably downgrade it, it MUST be bounced. 3. In the interest of interoperability, charsets other than UTF-8 are prohibited. There is no practical way to identify them properly with an extension similar to this without introducing great complexity. Klensin & Ko Expires December 25, 2006 [Page 7]
Internet-Draft EAI Framework June 2006 Conformance to the group of standards specified here for email transport and delivery requires implementation of the SMTP Extension specification, including recognition of the keywords associated with alternate and synthesized addresses, and the UTF-8 Header specification. Support for downgrading is not required, but, if implemented, MUST be implemented as specified. 4.2. Transmission of Email Header in UTF-8 Encoding There are many places in MUAs or in user presentation in which email addresses or domain names appear. Examples include the conventional From, To, or Cc header fields; Message-IDs; In-Reply-To fields that may contain addresses or domain names; in message bodies; or elsewhere. We must examine all of them from an internationalization perspective. The user will expect to see mailbox and domain names in local characters, and to see them consistently. If non-obvious encodings, such as protocol-specific ACE variants, are used, the user will inevitably see them, at least occasionally, rather than "native" characters and will find that discomfiting or astonishing. Similarly, if different codings are used for mail transport and message bodies, the user is particularly likely to be surprised, if only as a consequence of the long-established "things leak" principle. But the only practical way to avoid these sources of discomfort, in both the medium and the longer term, is to have the encodings used in transport be as nearly as possible the same as the encodings used in message headers and message bodies. It seems clear that the point at which email local parts are internationalized is the point that email headers should simply be shifted to a full internationalized form, presumably using UTF-8 rather than ASCII as the base character set for other than protocol elements such as the header field names themselves. The transition to that model includes support for address, and address-related, fields within the headers of legacy systems. This is done by extending the encoding models of [RFC2045] and [RFC2231]. However, our target should be fully internationalized headers, as discussed [I18Nemail-UTF8]. 4.3. Downgrading Mechanism for Backward Compatibility As with any use of the SMTP extension mechanism, there is always a possibility of a client that requires the feature encountering a server that does not. In the case of email address and header internationalization, the risk should be minimized by the fact that the selection of submission servers are presumably under the control of the sender's client and the selection of potential intermediate relays is under the control of the administration of the final delivery server. Klensin & Ko Expires December 25, 2006 [Page 8]
Internet-Draft EAI Framework June 2006 For those situations, there are basically two possibilities: o Reject or bounce the message, requiring the sender to resubmit it with traditional-format addresses and headers. o Figure out a way to downgrade the envelope or message body in transit. Especially when internationalized addresses are involved, downgrading will require either that an all-ASCII address be obtained from some source or computed. An optional extension parameter is provided as a way of transmitting an alternate address. Computing an all-ASCII form of a non-ASCII address requires that the sender have some knowledge. This knowledge is normally restricted to final delivery servers, but some extensions may be feasible there too. Downgrade issues and a specification are discussed in [I18Nemail-downgrade]. The first of these two options, that of rejecting or returning the message to the sender MAY always be chosen. There is also a third case, one in which the client is I18Nemail- capable, the server is not, but the message does not require the extended capabilities. In other words, both the addresses in the envelope and the entire set of headers of the message are entirely in ASCII (perhaps including encoded-words in the headers). In that case, the client SHOULD send the message whether or not the server announces the capability specified here. 5. Downgrading Before and After SMTP Transactions In addition to the in-transit downgrades discussed above, downgrading may also occur before or during initial message submission or after delivery to the final delivery MTA. Because these cases have a different set of available information from in-transit cases, the constraints and opportunities may be somewhat different too. These two cases are discussed in the subsections below. 5.1. Downgrading Before or During Message Submission Perhaps obviously, the most convenient time to convert an address or message from internationalized to conventional ASCII form is at the originating MUA, either before the message is sent or after the internationalized form of the message is rejected or bounced by some MTA in the path to the presumed destination. At that point, the user has a full range of choices available, including contacting the intended recipient out of band for an alternate address, consulting appropriate directories, arranging for translation of both addresses and message content into a different language, and so on. While it is natural to think of message downgrading as optimally being a fully-automated process, we should not underestimate the capabilities Klensin & Ko Expires December 25, 2006 [Page 9]
Internet-Draft EAI Framework June 2006 of a user of at least moderate intelligence who wishes to communicate with another such user. In this context, one can easily imagine modifications to message submission servers (as described in RFC 4409 [RFC4409]) so that they would perform downgrading, or perhaps even upgrading, operations, receiving messages with one or more of the internationalization extensions discussed here and adapting the outgoing message, as needed, to respond to the delivery or next-hop environment it encounters. 5.2. Downgrading or Other Processing After Final SMTP Delivery When an email message is received by a final delivery SMTP server, it is usually stored in some form. Then it is retrieved by client software via some email retrieval mechanisms such as POP, IMAP or others. The SMTP extension described in Section 4.1 provides protection only in transport. It does not prevent MUAs and email retrieval mechanisms that have not been upgraded to understand internationalized addresses and UTF-8 headers from accessing stored internationalized emails. Since the final delivery SMTP server (to be more specific, its corresponding mail storage agent) cannot safely assume that agents accessing email storage will be always be capable of handling the extensions proposed here, it MAY either downgrade internationalized emails or specially identify messages that utilize these extensions, or both. If this is the case, the final delivery SMTP server MUST include a mechanism to preserve the original internationalized forms without information loss to support access by I18Nemail-aware agents. The method and format for downgrading at the final delivery SMTP server is [[anchor13: will be]] discussed in [I18Nemail-pop] and [I18Nemail-imap]. [[anchor14: Note in draft: There are at least four cases. Both MUA and IMAP/POP are compliant. Both are non compliant. And only of them is compliant. Do we need to invent different methods for each case?]] 6. Advice to Designers and Operators of Mail-receiving Systems [[anchor16: Note in draft: The material that follows contains some forward-looking, predictive, statements about discussions to occur and documents to be written. Be sure they are true before Last Klensin & Ko Expires December 25, 2006 [Page 10]
Internet-Draft EAI Framework June 2006 Call.]] In addition to the protocol specification materials in this set of documents, the working group has had extensive discussions about operational considerations in the use of internationalized addresses. Those topics include how such addresses should be chosen, how they should relate to ASCII alternatives if such alternatives exist, the management of mailing lists that might support and contain a mixture of all-ASCII and non-ASCII addresses, and so on. Those issues are discussed in [I18Nemail-Exploder]. 7. Internationalization Considerations This entire specification addresses issues in internationalization and especially the boundaries between internationalization and localization and between network protocols and client/user interface actions. 8. Additional Issues This section identifies issues that are not covered as part of this set of specifications, but that will need to be considered as part of deployment of email address and header internationalization. 8.1. Impact on IRIs The mailto: schema defined in [RFC2368] and discussed in IRI [RFC3987] may need to be modified when this work is completed and standardized. 8.2. POP and IMAP While SMTP takes care of the transportation of messages, IMAP [RFC3501] and POP3 [RFC1939] are among mechanisms used to handle the retrieval of mail objects from a mail store by a client. The use of internationalized mail addresses or UTF-8 headers will require extensions to POP and IMAP and/or modifications to the design and implementation of mail stores and the mechanisms that final delivery SMTP servers use to put mail into them. However, those mechanisms are separate from those associated with transport across the network and are discussed only minimally in this series of documents. The general issues, and proposed required modifications to the protocols, are [[anchor21: will be]] covered in [I18Nemail-pop] and [I18Nemail- imap]. Some preliminary discussion appears in in Section 5.2. Implementation of internationalized POP and IMAP support is, of course, not required for implementation of the transport and in- Klensin & Ko Expires December 25, 2006 [Page 11]
Internet-Draft EAI Framework June 2006 transit header extensions specified in other documents or this set (or vica versa). 9. Experimental Targets In addition to the simple question of whether the model outlined here can be made to work in a satisfactory way for upgraded systems and provide adequate protection for un-upgraded ones, we expect that actually working with the systems will provide answers to two additional questions: what restrictions such as character lists or normalization should be placed, if any, on the characters that are permitted to be used in address local-parts and how useful, in practice, will downgrading turn out to be given whatever restrictions and constraints that must be placed upon it. 10. IANA Considerations This overview description and framework document does not contemplate any IANA registrations or other actions. Some of the documents in the group have their own IANA considerations sections and requirements. 11. Security Considerations Any expansion of permitted characters and encoding forms in email addresses raises some risks. There have been discussions on so called "IDN-spoofing" or "IDN homograph attacks". These attacks allow an attacker (or "phisher") to spoof the domain or URLs of businesses. The same kind of attack is also possible on the local part of internationalized email addresses. It should be noted that one of the proposed fixes for, e.g., URLs, does not work for email local parts since they are case-sensitive. That fix involves forcing all elements that are displayed to be in lower-case and normalized. Since email addresses are often transcribed from business cards and notes on paper, they are subject to problems arising from confusable characters. These problems are somewhat reduced if the domain associated with the mailbox is unambiguous and supports a relatively small number of mailboxes whose names follow local system conventions; they are increased with very large mail systems in which users can freely select their own addresses. The internationalization of email addresses and headers must not leave the Internet less secure than it is that without the required extensions. The requirements and mechanisms documented in this set Klensin & Ko Expires December 25, 2006 [Page 12]
Internet-Draft EAI Framework June 2006 of specifications do not, in general, raise any new security issues. They do require a review of issues associated with confusable characters -- a topic that is being explored thoroughly elsewhere [IDN-nextsteps] -- and, potentially, some issues with UTF-8 canonicalization, discussed in [RFC3629]. The latter is also part of the subject of ongoing work discussed in [Net-Unicode]. Specific issues are discussed in more detail in the other documents in this set. However, in particular, caution should be taken that any "downgrading" mechanism, or use of downgraded addresses, does not inappropriately assume authenticated bindings between the internationalized and ASCII addresses. In addition, email addresses are used in many contexts other than sending mail, such as for identifiers under various circumstances. Each of those contexts will need to be evaluated, in turn, to determine whether the use of non-ASCII forms is appropriate and what particular issues they raise. This work will clearly impact any systems or mechanisms that is dependent on digital signatures or similar integrity protection for mail headers. Conventional uses of PGP and S/MIME are not affected since they are used to sign body parts but not headers. On the other hand, the developing work in DKIM will eventually need to consider this work and vice versa: while this experiment does not propose to address or solve the issues raised by DKIM and other signed header mechanisms, the issues will have to be coordinated and resolved eventually. 12. Acknowledgements This document, and the related ones, were originally derived from drafts by John Klensin and the JET group [Klensin-emailaddr], [JET- IMA]. The work drew inspiration from discussions on the "IMAA" mailing list, sponsored by the Internet Mail Consortium and especially from an early draft by Paul Hoffman and Adam Costello [Hoffman-IMAA] that attempted to define an MUA-only solution to the address internationalization problem. [[anchor25: Note in draft: may want to move some of this to "history" or reference it]] 13. Change History [[anchor27: This section to be restructured prior to publication. It may be useful to retain parts of it to facilitate establishing dates and documents for the history of this work.]] This document has evolved through several titles as well as the usual Klensin & Ko Expires December 25, 2006 [Page 13]
Internet-Draft EAI Framework June 2006 version numbers. The list below tries to trace that thread as well as changes within the substance of the document. The first document of the series was posted as draft-klensin-emailaddr-i18n-00.txt in October 2003. 13.1. draft-klensin-ima-framework: Version 00 This version supercedes draft-lee-jet-ima-00 and draft-klensin-emailaddr-i18n-03. It represents a major rewrite and change of architecture from the former and incorporates many ideas and some text from the latter. 13.2. draft-klensin-ima-framework: Version 01 o Some clarifications of terminology (more to follow) and general editorial improvements. o Upgrades to reflect discussions during IETF 64. o Improved treatment of downgrading before and after message transport. 13.3. draft-ietf-eai-framework: Version 00 This version supercedes draft-klensin-ima-framework-01; its file name should represent the form to be used until the IETF email address and header internationalization ("EAI") work concludes. o Changed "display name" terminology to be consistent with RFC 2822. Also clarified some other terminology issues. o Added a comment about the possible role of MessageSubmission servers in downgrading. o Removed the "IMA" terminology, converting it to either "EAI" or prose. o Per meeting and mailing list discussion, added conformance statements about bouncing if neither forwarding nor downgrading were possible and about implementation requirements. o Updated several references. Some documents are still tentative. o Fixed many typographical errors. 13.4. draft-ietf-eai-framework: Version 01 o Added comments about PGP, S/MIME, and DKIM to Security Considerations o Rationalized terminology and included terminology from scenarios document. 14. References Klensin & Ko Expires December 25, 2006 [Page 14]
Internet-Draft EAI Framework June 2006 14.1. Normative References [ASCII] American National Standards Institute (formerly United States of America Standards Institute), "USA Code for Information Interchange", ANSI X3.4-1968, 1968. ANSI X3.4-1968 has been replaced by newer versions with slight modifications, but the 1968 version remains definitive for the Internet. [I18Nemail-Exploder] Chung, E., "Mailing lists and internationalized email addresses", June 2006. Forthcoming [I18Nemail-SMTPext] Yao, J., Ed. and X. Lee, Ed., "SMTP extension for internationalized email address", draft-ietf-eai-smtpext-00 (work in progress), January 2006. [I18Nemail-UTF8] Yeh, J., "Transmission of Email Headers in UTF-8 Encoding", draft-ietf-eai-utf8headers-00.txt (work in progress), June 2006. [I18Nemail-downgrade] YONEYA, Y., Ed. and K. Fujiwara, Ed., "Downgrading mechanism for Internationalized eMail Address (IMA)", draft-ietf-eai-downgrade-00 (work in progress), October 2005. [RFC1652] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D. Crocker, "SMTP Service Extension for 8bit-MIMEtransport", RFC 1652, July 1994. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels'", RFC 2119, March 1997. [RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April 2001. [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing Domain Names in Applications (IDNA)", RFC 3490, March 2003. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO Klensin & Ko Expires December 25, 2006 [Page 15]
Internet-Draft EAI Framework June 2006 10646", STD 63, RFC 3629, November 2003. 14.2. Informative References [Hoffman-IMAA] Hoffman, P. and A. Costello, "Internationalizing Mail Addresses in Applications (IMAA)", draft-hoffman-imaa-03 (work in progress), October 2003. [I18Nemail-constraints] Klensin, J., "Internationalization in Internet Applications: Issues, Tradeoffs, and Email Addresses", February 2006. [I18Nemail-history] Klensin, J., "Decisions and Alternatives for Internationalization of Email Addresses", April 2006. This document is expected to be developed separately from the WG. The date given here is purely arbitrary. [I18Nemail-imap] Resnick, P. and C. Newman, "Considerations for IMAP in Conjunction with Email Address Internationalization", draft-ietf-eai-imap-utf8-00 (work in progress), May 2006. [I18Nemail-pop] Newman, C., "POP3 Support for UTF-8", February 2006, <http ://www.ietf.org/internet-drafts/ draft-newman-ima-pop-00.txt>. The next version of this document will appear as draft-ietf-eai-pop-00.txt. [I18Nemail-scenarios] Alvestrand, H., "Internationalized Email Addresses: Scenarios", draft-ietf-eai-scenarios-00 (work in progress), May 2006. [IDN-nextsteps] Klensin, J. and P. Faltstrom, "Review and Recommendations for Internationalized Domain Names (IDN)", April 2006, <ht tp://www.ietf.org/internet-drafts/ draft-iab-idn-nextsteps-05.txt>. [JET-IMA] Yao, J. and J. Yeh, "Internationalized eMail Address (IMA)", draft-lee-jet-ima-00 (work in progress), June 2005. Klensin & Ko Expires December 25, 2006 [Page 16]
Internet-Draft EAI Framework June 2006 [Klensin-emailaddr] Klensin, J., "Internationalization of Email Addresses", draft-klensin-emailaddr-i18n-03 (work in progress), July 2005. [Net-Unicode] Klensin, J. and M. Padlipsky, "Unicode Format for Network Interchange", April 2006, <http://www.ietf.org/ internet-drafts/draft-klensin-net-utf8-00.txt>. [RFC1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3", STD 53, RFC 1939, May 1996. [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text", RFC 2047, November 1996. [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations", RFC 2231, November 1997. [RFC2368] Hoffman, P., Masinter, L., and J. Zawinski, "The mailto URL scheme", RFC 2368, July 1998. [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April 2001. [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1", RFC 3501, March 2003. [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, January 2005. [RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail", RFC 4409, April 2006. Klensin & Ko Expires December 25, 2006 [Page 17]
Internet-Draft EAI Framework June 2006 Authors' Addresses John C Klensin 1770 Massachusetts Ave, #322 Cambridge, MA 02140 USA Phone: +1 617 491 5735 Email: john-ietf@jck.com YangWoo Ko MOCOCO, Inc. 996-1, 11F, Mirae Asset Venture Tower, Daechi-dong Gangnam-gu, Seoul 135-280 Korea Email: yw@mrko.pe.kr Klensin & Ko Expires December 25, 2006 [Page 18]
Internet-Draft EAI Framework June 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Klensin & Ko Expires December 25, 2006 [Page 19]