Network Working Group J. Klensin
Request for Comments: 4952
Category: Informational Y. Ko
ICU
July 2007
Network Working Group J. Klensin
Request for Comments: 4952
Category: Informational Y. Ko
ICU
July 2007
Overview and Framework for Internationalized Email
国际化电子邮件的概述和框架
Status of This Memo
关于下段备忘
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
本备忘录为互联网社区提供信息。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The IETF Trust (2007).
版权所有（C）IETF信托基金（2007年）。
Abstract
摘要
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 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.
在全世界范围内充分使用电子邮件要求人们能够在电子邮件地址中使用用自己的语言和脚本正确书写的自己的姓名作为邮箱名称。本文档介绍了一系列规范，这些规范定义了完全支持国际化电子邮件地址所需的机制和协议扩展。这些更改包括SMTP扩展和电子邮件头语法扩展，以适应UTF-8数据。该文档集还包括对部署完全国际化电子邮件的关键假设和问题的讨论。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Role of This Specification . . . . . . . . . . . . . . . . 3
1.2. Problem Statement . . . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Overview of the Approach . . . . . . . . . . . . . . . . . . . 6
3. Document Plan . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Overview of Protocol Extensions and Changes . . . . . . . . . 7
4.1. SMTP Extension for Internationalized Email Address . . . . 7
4.2. Transmission of Email Header Fields in UTF-8 Encoding . . 8
4.3. Downgrading Mechanism for Backward Compatibility . . . . . 9
5. Downgrading before and after SMTP Transactions . . . . . . . . 10
5.1. Downgrading before or during Message Submission . . . . . 10
5.2. Downgrading or Other Processing After Final SMTP
Delivery . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Additional Issues . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Impact on URIs and IRIs . . . . . . . . . . . . . . . . . 11
6.2. Interaction with Delivery Notifications . . . . . . . . . 12
6.3. Use of Email Addresses as Identifiers . . . . . . . . . . 12
6.4. Encoded Words, Signed Messages, and Downgrading . . . . . 12
6.5. Other Uses of Local Parts . . . . . . . . . . . . . . . . 13
6.6. Non-Standard Encapsulation Formats . . . . . . . . . . . . 13
7. Experimental Targets . . . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . . 16
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Role of This Specification . . . . . . . . . . . . . . . . 3
1.2. Problem Statement . . . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Overview of the Approach . . . . . . . . . . . . . . . . . . . 6
3. Document Plan . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Overview of Protocol Extensions and Changes . . . . . . . . . 7
4.1. SMTP Extension for Internationalized Email Address . . . . 7
4.2. Transmission of Email Header Fields in UTF-8 Encoding . . 8
4.3. Downgrading Mechanism for Backward Compatibility . . . . . 9
5. Downgrading before and after SMTP Transactions . . . . . . . . 10
5.1. Downgrading before or during Message Submission . . . . . 10
5.2. Downgrading or Other Processing After Final SMTP
Delivery . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Additional Issues . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Impact on URIs and IRIs . . . . . . . . . . . . . . . . . 11
6.2. Interaction with Delivery Notifications . . . . . . . . . 12
6.3. Use of Email Addresses as Identifiers . . . . . . . . . . 12
6.4. Encoded Words, Signed Messages, and Downgrading . . . . . 12
6.5. Other Uses of Local Parts . . . . . . . . . . . . . . . . 13
6.6. Non-Standard Encapsulation Formats . . . . . . . . . . . . 13
7. Experimental Targets . . . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . . 16
In order to use internationalized email addresses, we need to internationalize both the domain part and the local part of email addresses. The domain part of email addresses is already internationalized [RFC3490], while the local part is not. Without the extensions specified in this document, the mailbox name is restricted to a subset of 7-bit ASCII [RFC2821]. Though MIME [RFC2045] enables the transport of non-ASCII data, it does not provide a mechanism for internationalized email addresses. In RFC 2047 [RFC2047], MIME defines an encoding mechanism for some specific message header fields to accommodate non-ASCII data. However, it does not permit the use 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 any part of email addresses is to use RFC 2047 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. Information coded into the display name is invisible in the message envelope and, for many purposes, is not part of the address at all.
为了使用国际化的电子邮件地址，我们需要对电子邮件地址的域部分和本地部分进行国际化。电子邮件地址的域部分已国际化[RFC3490]，而本地部分未国际化。如果没有本文档中指定的扩展名，邮箱名称仅限于7位ASCII[RFC2821]的子集。尽管MIME[RFC2045]支持非ASCII数据的传输，但它不提供国际化电子邮件地址的机制。在RFC 2047[RFC2047]中，MIME为一些特定的消息头字段定义了一种编码机制，以容纳非ASCII数据。但是，它不允许使用包含非ASCII字符的电子邮件地址。如果没有此处定义的扩展名或某些等效集，在电子邮件地址的任何部分中包含非ASCII字符的唯一方法是使用RFC 2047编码将它们嵌入到RFC 2822[RFC2822]所称的相关标题的“显示名称”（称为“名称短语”或其他术语）。编码到显示名称中的信息在消息信封中是不可见的，并且出于许多目的，根本不是地址的一部分。
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.
本文档介绍了电子邮件国际化下一阶段方法的概述和框架。这个新阶段不仅需要地址和头的国际化，还需要相关的传输和交付模型。
This document provides the framework for a series of experimental specifications that, together, provide the details for a way to implement and support internationalized email. The document itself describes how the various elements of email internationalization fit together and how the relationships among the various documents are involved.
本文档提供了一系列实验性规范的框架，这些规范一起提供了实现和支持国际化电子邮件的详细信息。文档本身描述了电子邮件国际化的各种元素如何结合在一起，以及各种文档之间的关系如何涉及。
Internationalizing Domain Names in Applications (IDNA) [RFC3490] permits internationalized domain names, but deployment has not yet reached most users. One of the reasons for this is that we do not yet have fully internationalized naming schemes. Domain names are just one of the various names and identifiers that are required to be internationalized. In many contexts, until more of those identifiers are internationalized, internationalized domain names alone have little value.
应用程序中的域名国际化（IDNA）[RFC3490]允许域名国际化，但大多数用户尚未使用。其中一个原因是我们还没有完全国际化的命名方案。域名只是需要国际化的各种名称和标识符之一。在许多情况下，在更多的标识符国际化之前，国际化域名本身没有什么价值。
Email addresses are prime examples of why it is not good enough to just internationalize the domain name. As most of us have learned
电子邮件地址是为什么仅仅国际化域名还不够好的主要例子。我们大多数人都知道
from experience, users strongly prefer email addresses that resemble names or initials to those involving seemingly meaningless strings of letters or numbers. Unless the entire email address can use familiar characters and formats, users will perceive email as being culturally unfriendly. If the names and initials used in email addresses can be expressed in the native languages and writing systems of the users, the Internet will be perceived as more natural, especially by those whose native language is not written in a subset of a Roman-derived script.
根据经验，用户强烈喜欢类似姓名或首字母的电子邮件地址，而不喜欢包含看似毫无意义的字母或数字字符串的电子邮件地址。除非整个电子邮件地址可以使用熟悉的字符和格式，否则用户会认为电子邮件在文化上不友好。如果电子邮件地址中使用的姓名和首字母可以用用户的母语和书写系统表达，互联网将被视为更加自然，尤其是那些母语不是用罗马衍生脚本子集书写的人。
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 respond by displaying local characters. To be perceived as usable, the addresses must be internationalized and handled consistently in all of the contexts in which they occur. This requirement has far-reaching implications: collections of patches and workarounds are not adequate. Even if they were adequate, a workaround-based approach may result in an assortment of implementations with different sets of patches and workarounds having been applied with consequent user confusion about what is actually usable 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. 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 SMTP extension [RFC1652] so that all of these can be transported through the mail system without having to overcome the limitation that headers do not have content-transfer-encodings.
电子邮件地址的国际化不仅仅是更改SMTP信封的问题；或者修改From、To和Cc头；或者允许升级的邮件用户代理（MUA）解码特殊编码并通过显示本地字符进行响应。要被认为是可用的，地址必须国际化，并在它们出现的所有上下文中一致地处理。这一要求有着深远的影响：补丁和解决方案的集合是不够的。即使它们是足够的，基于解决方案的方法可能会导致应用了不同补丁集和解决方案的各种实现，从而导致用户对什么是实际可用和支持的感到困惑。相反，我们需要建立一个完全国际化的电子邮件环境，重点是允许那些共享一种语言或其他社区的人之间进行有效沟通。这反过来意味着对邮件头环境的更改，以允许在有意义的情况下使用全部Unicode字符，SMTP扩展允许UTF-8[RFC3629]邮件寻址和传递这些扩展头，以及（最后）支持8BITMIME SMTP扩展[RFC1652]的要求因此，所有这些都可以通过邮件系统进行传输，而无需克服标头没有内容传输编码的限制。
This document assumes a reasonable understanding of the protocols and terminology of the core email standards as documented in [RFC2821] and [RFC2822].
本文件假设合理理解[RFC2821]和[RFC2822]中记录的核心电子邮件标准的协议和术语。
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 application of the "protocols on the wire" principle to it. 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).
本文档中的大部分描述依赖于“邮件传输代理”（“MTA”）和“邮件用户代理”（“MUA”）的抽象。然而，重要的是要理解，这些术语和基本概念追溯到互联网电子邮件体系结构的设计和“在线协议”原则的应用。随着电子邮件体系结构的发展，以及“连线”原则，使得MTA和MUA在给定的源主机或目标主机（甚至是它们是否分开）上的交互方式没有任何明显的标准化区别。
However, the term "final delivery MTA" is used in this document in a fashion equivalent to the term "delivery system" or "final delivery system" of RFC 2821. This is the SMTP server that controls the format of the local parts of addresses and is permitted to inspect and interpret them. It receives messages from the network for delivery to mailboxes or for other local processing, including any forwarding or aliasing that changes envelope addresses, rather than relaying. From the perspective of the network, any local delivery arrangements such as saving to a message store, handoff to specific message delivery programs or agents, and mechanisms for retrieving messages are all "behind" the final delivery MTA and hence are not part of the SMTP transport or delivery process.
但是，本文件中使用的术语“最终交付MTA”与RFC 2821中的术语“交付系统”或“最终交付系统”相同。这是SMTP服务器，控制地址的本地部分的格式，并允许检查和解释它们。它接收来自网络的消息，以便发送到邮箱或进行其他本地处理，包括更改信封地址的任何转发或别名，而不是中继。从网络的角度来看，任何本地传递安排（如保存到邮件存储、切换到特定邮件传递程序或代理以及检索邮件的机制）都是在最终传递MTA之后，因此不属于SMTP传输或传递过程的一部分。
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 "i18n-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 to this definition. The term "all-ASCII" is also applied to other protocol elements when the distinction is important, with "non-ASCII" or "internationalized" as its opposite.
在本文档中，如果地址中的每个字符都在ASCII字符表[ASCII]中，则地址为“全部ASCII”，或仅为“ASCII地址”；如果ASCII字符表中没有任何字符，则地址为“非ASCII”或“i18n地址”。此类地址可能会受到其他方式的限制，但这些限制与本定义无关。当区分很重要时，术语“所有ASCII”也适用于其他协议元素，与之相对的是“非ASCII”或“国际化”。
The umbrella term to describe the email address internationalization specified by this document and its companion documents is "UTF8SMTP". For example, an address permitted by this specification is referred to as a "UTF8SMTP (compliant) address".
描述本文档及其附带文档指定的电子邮件地址国际化的总称为“UTF8SMTP”。例如，本规范允许的地址称为“UTF8SMTP（兼容）地址”。
Please note that, according to the definitions given here, the set of all "all-ASCII" addresses and the set of all "non-ASCII" addresses are mutually exclusive. The set of all UTF8SMTP addresses is the union of these two sets.
请注意，根据此处给出的定义，所有“所有ASCII”地址集和所有“非ASCII”地址集是互斥的。所有UTF8SMTP地址的集合是这两个集合的并集。
An "ASCII user" (i) exclusively uses email addresses that contain ASCII characters only, and (ii) cannot generate recipient addresses that contain non-ASCII characters.
“ASCII用户”（i）只使用仅包含ASCII字符的电子邮件地址，（ii）无法生成包含非ASCII字符的收件人地址。
An "i18mail user" has one or more non-ASCII email addresses. Such a user may have ASCII addresses too; if the user has more than one email account and a corresponding address, or more than one alias for the same address, he or she has some method to choose which address to use on outgoing email. Note that under this definition, it is not possible to tell from an ASCII address if the owner of that address is an i18mail user or not. (A non-ASCII address implies a belief that the owner of that address is an i18mail user.) There is no such thing as an "i18mail message"; the term applies only to users and their agents and capabilities.
“i18mail用户”有一个或多个非ASCII电子邮件地址。这样的用户也可能有ASCII地址；如果用户有多个电子邮件帐户和相应的地址，或者同一地址有多个别名，则用户可以通过某种方法选择在发送电子邮件时使用的地址。请注意，根据此定义，无法从ASCII地址判断该地址的所有者是否为i18mail用户。（非ASCII地址意味着相信该地址的所有者是i18mail用户。）没有“i18mail消息”这样的东西；该术语仅适用于用户及其代理和功能。
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").
“消息”从一个用户（发件人）使用特定的电子邮件地址发送到一个或多个其他收件人电子邮件地址（通常称为“用户”或“收件人用户”）。
A "mailing list" is a mechanism whereby a message may be distributed to multiple recipients by sending it 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. This agent sets the envelope return address of the redistributed message to a different address from that of the original single recipient message. Using a different envelope return address (reverse-path) causes error (and other automatically generated) messages to go to an error handling address.
“邮件列表”是一种机制，通过将邮件发送到一个收件人地址，可以将邮件分发给多个收件人。然后，位于该地址的代理（通常不是人）会将邮件重新分发给目标收件人。此代理将重新分发邮件的信封返回地址设置为与原始单个收件人邮件不同的地址。使用不同的信封返回地址（反向路径）会导致错误（和其他自动生成的）消息转到错误处理地址。
As specified in RFC 2821, a message that is undeliverable for some reason is expected to result in notification to the sender. This can occur in either of two ways. One, typically called "Rejection", occurs when an SMTP server returns a reply code indicating a fatal error (a "5yz" code) or persistently returns a temporary failure error (a "4yz" code). The other involves accepting the message during SMTP processing and then generating a message to the sender, typically known as a "Non-delivery Notification" or "NDN". Current practice often favors rejection over NDNs because of the reduced likelihood that the generation of NDNs will be used as a spamming technique. The latter, NDN, case is unavoidable if an intermediate MTA accepts a message that is then rejected by the next-hop server.
如RFC 2821中所述，由于某种原因无法传递的消息预计会导致通知发送方。这可以通过两种方式之一发生。当SMTP服务器返回指示致命错误的回复代码（“5yz”代码）或持续返回临时故障错误（“4yz”代码）时，会发生一种通常称为“拒绝”的情况。另一种是在SMTP处理过程中接受邮件，然后向发件人生成邮件，通常称为“未送达通知”或“NDN”。目前的做法通常倾向于拒绝NDN，因为生成NDN作为垃圾邮件技术的可能性降低。如果中间MTA接受消息，然后被下一跳服务器拒绝，则后一种情况（NDN）是不可避免的。
The pronouns "he" and "she" are used interchangeably to indicate a human of indeterminate gender.
代词“他”和“她”交替使用，表示性别不确定的人。
The key words "MUST", "SHALL", "REQUIRED", "SHOULD", "RECOMMENDED", and "MAY" in this document are to be interpreted as described in RFC 2119 [RFC2119].
本文件中的关键词“必须”、“应”、“要求”、“应”、“建议”和“可能”应按照RFC 2119[RFC2119]中的说明进行解释。
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 implementation suggestions and guidance for the protocols.
这组规范更改了SMTP和电子邮件头的格式，以允许直接表示非ASCII字符。工作的每个重要组成部分在单独的文件中描述。文档集的成员将在下一节中介绍，文档集还包含信息性文档，其目的是为协议提供实施建议和指导。
In addition to this document, the following documents make up this specification and provide advice and context for it.
除本文件外，以下文件构成本规范，并为其提供建议和上下文。
o SMTP extensions. This document [EAI-SMTPext] provides an SMTP extension for internationalized addresses, as provided for in RFC 2821.
o SMTP扩展。此文档[EAI SMTPext]为RFC 2821中提供的国际化地址提供SMTP扩展。
o Email headers in UTF-8. This document [EAI-UTF8] 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 described above is used. This document, possibly with one or more supplemental ones, will also need to address the interactions with MIME, including relationships between UTF8SMTP and internal MIME headers and content types.
o UTF-8中的电子邮件标题。本文档[EAI-UTF8]实质上更新了RFC 2822，以允许在使用上述SMTP扩展时，电子邮件头中的某些信息直接由UTF-8编码的Unicode字符表示。本文档（可能有一个或多个补充文档）还需要解决与MIME的交互，包括UTF8SMTP与内部MIME头和内容类型之间的关系。
o In-transit downgrading from internationalized addressing with the SMTP extension and UTF-8 headers to traditional email formats and characters [EAI-downgrade]. Downgrading either at the point of message origination or after the mail has successfully been received by a final delivery SMTP server involve different constraints and possibilities; see Section 4.3 and Section 5, below. Processing that occurs after such final delivery, particularly processing that is involved with the delivery to a mailbox or message store, is sometimes called "Message Delivery" processing.
o 在传输过程中，从使用SMTP扩展名和UTF-8头的国际化寻址降级为传统电子邮件格式和字符[EAI降级]。无论是在邮件发起点还是在最终传递SMTP服务器成功接收邮件后，降级都涉及不同的限制和可能性；见下文第4.3节和第5节。在这样的最终传递之后发生的处理，特别是和传递到邮箱或消息存储有关的处理，有时称为“消息传递”处理。
o Extensions to the IMAP protocol to support internationalized headers [EAI-imap].
o 对IMAP协议的扩展，以支持国际化标头[EAI IMAP]。
o Parallel extensions to the POP protocol [EAI-pop].
o POP协议的并行扩展[EAI POP]。
o Description of internationalization changes for delivery notifications (DSNs) [EAI-DSN].
o 交付通知（DSN）国际化更改的说明[EAI-DSN]。
o Scenarios for the use of these protocols [EAI-scenarios].
o 这些协议的使用场景[EAI场景]。
An SMTP extension, "UTF8SMTP" is specified as follows:
SMTP扩展名“UTF8SMTP”指定如下：
o Permits the use of UTF-8 strings in email addresses, both local parts and domain names.
o 允许在电子邮件地址（本地部分和域名）中使用UTF-8字符串。
o Permits the selective use of UTF-8 strings in email headers (see Section 4.2).
o 允许在电子邮件头中选择性使用UTF-8字符串（见第4.2节）。
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 special content-transfer-encoding.
o 要求服务器播发8BITMIME扩展[RFC1652]，并且客户端支持8位传输，以便可以在不使用特殊内容传输编码的情况下传输头信息。
o Provides information to support downgrading mechanisms.
o 提供支持降级机制的信息。
Some general principles affect the development decisions underlying this work.
一些一般原则会影响这项工作背后的开发决策。
1. Email addresses enter subsystems (such as a user interface) that may perform charset conversions or other encoding changes. When the left hand side of the address includes characters outside the US-ASCII character repertoire, use of punycode on the right hand side is discouraged to promote consistent processing of characters throughout the address.
1. 电子邮件地址输入可能执行字符集转换或其他编码更改的子系统（如用户界面）。当地址的左侧包含US-ASCII字符表以外的字符时，不鼓励在右侧使用punycode，以促进整个地址中字符的一致处理。
2. An SMTP relay must
2. 必须使用SMTP中继
* Either recognize the format explicitly, agreeing to do so via an ESMTP option,
* 明确识别格式，同意通过ESMTP选项进行识别，
* Select and use an ASCII-only address, downgrading other information as needed (see Section 4.3), or
* 选择并使用仅ASCII地址，根据需要降级其他信息（见第4.3节），或
* Reject the message or, if necessary, return a non-delivery notification message, so that the sender can make another plan.
* 拒绝邮件，或在必要时返回未送达通知邮件，以便发件人可以制定其他计划。
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 rejected or a non-delivery message generated and sent.
如果消息无法转发，因为下一跳系统无法接受扩展，并且没有足够的信息来可靠地降级，则必须拒绝该消息，或者生成并发送未送达消息。
3. In the interest of interoperability, charsets other than UTF-8 are prohibited in mail addresses and headers. There is no practical way to identify them properly with an extension similar to this without introducing great complexity.
3. 为了实现互操作性，邮件地址和邮件头中禁止使用UTF-8以外的字符集。如果不引入极大的复杂性，那么使用类似于此的扩展来正确识别它们是没有实际方法的。
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 addresses, and the UTF-8 Header specification. Support for downgrading is not required, but, if implemented, MUST be implemented as specified. Similarly, if the system implements IMAP or POP, it MUST conform to the i18n IMAP or POP specifications respectively.
要符合此处为电子邮件传输和传递指定的一组标准，需要实施SMTP扩展规范，包括识别与备用地址相关的关键字，以及UTF-8标头规范。不需要支持降级，但如果实施，则必须按照规定实施。同样，如果系统实现IMAP或POP，则必须分别符合i18n IMAP或POP规范。
There are many places in MUAs or in a user presentation in which email addresses or domain names appear. Examples include the conventional From, To, or Cc header fields; Message-ID and In-Reply-To header fields that normally contain domain names (but that may be a special case); and in message bodies. Each of these must be examined 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 ASCII-Compatible Encoding (ACE) variants, are used, the user will inevitably, if only occasionally, see them 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. 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 similar to the encodings used in message headers and message bodies as possible.
MUAs或用户演示文稿中有许多地方显示电子邮件地址或域名。示例包括传统的From、To或Cc报头字段；消息ID和回复头字段通常包含域名（但这可能是一种特殊情况）；以及在消息体中。每一项都必须从国际化的角度来审视。用户将期望看到本地字符的邮箱和域名，并一致地看到它们。如果使用非明显的编码，例如协议特定的ASCII兼容编码（ACE）变体，用户将不可避免地（即使只是偶尔）看到它们而不是“本机”字符，并会发现这令人不安或惊讶。类似地，如果邮件传输和消息正文使用不同的编码，那么用户尤其可能会感到惊讶，如果这仅仅是长期存在的“东西泄漏”原则的结果。从中期和长期来看，避免这些不适源的唯一实用方法是使传输中使用的编码尽可能类似于消息头和消息体中使用的编码。
When email local parts are internationalized, it seems clear that they should be accompanied by arrangements for the email headers to be in the fully internationalized form. That form should presumably use UTF-8 rather than ASCII as the base character set for the contents of header fields (protocol elements such as the header field names themselves will remain entirely in ASCII). For transition purposes and compatibility with legacy systems, this can done by extending the encoding models of [RFC2045] and [RFC2231]. However, our target should be fully internationalized headers, as discussed in [EAI-UTF8].
当电子邮件本地部分国际化时，很明显，它们应该伴随着电子邮件标题以完全国际化的形式的安排。该表单应该使用UTF-8而不是ASCII作为头字段内容的基本字符集（协议元素，例如头字段名称本身将完全保留为ASCII）。为了实现转换和与遗留系统的兼容性，可以通过扩展[RFC2045]和[RFC2231]的编码模型来实现。然而，我们的目标应该是完全国际化的头，如[EAI-UTF8]中所讨论的。
As with any use of the SMTP extension mechanism, there is always the possibility of a client that requires the feature encountering a server that does not support the required feature. 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.
与任何SMTP扩展机制的使用一样，需要该功能的客户端总是可能遇到不支持该功能的服务器。在电子邮件地址和邮件头国际化的情况下，应通过以下事实将风险降至最低：提交服务器的选择可能由发件人的客户端控制，潜在中间中继的选择由最终交付服务器的管理控制。
For situations in which a client that needs to use UTF8SMTP encounters a server that does not support the extension UTF8SMTP, there are two possibilities:
对于需要使用UTF8SMTP的客户端遇到不支持UTF8SMTP扩展的服务器的情况，有两种可能性：
o Reject the message or generate and send a non-delivery message, requiring the sender to resubmit it with traditional-format addresses and headers.
o 拒绝邮件或生成并发送未送达邮件，要求发件人使用传统格式的地址和邮件头重新提交邮件。
o Figure out a way to downgrade the envelope or message body in transit. Especially when internationalized addresses are involved, downgrading will require that all-ASCII addresses be obtained from some source. An optional extension parameter is provided as a way of transmitting an alternate address. Downgrade issues and a specification are discussed in [EAI-downgrade].
o 找出一种在传输过程中降级信封或邮件正文的方法。特别是当涉及国际化地址时，降级将要求从某个来源获取所有ASCII地址。提供可选扩展参数作为传输备用地址的方式。降级问题和规范在[EAI降级]中讨论。
(The client can also try an alternate next-hop host or requeue the message and try later, on the assumption that the lack of UTF8SMTP is a transient failure; since this ultimately resolves to success or failure, it doesn't change the discussion here.)
（客户端还可以尝试备用下一跳主机，或者重新获取消息，稍后再试，前提是缺少UTF8SMTP是暂时性故障；因为这最终会导致成功或失败，因此不会改变此处的讨论。）
The first of these two options, that of rejecting or returning the message to the sender MAY always be chosen.
这两个选项中的第一个选项，即拒绝或将邮件返回给发件人，可以始终选择。
If a UTF8SMTP capable client is sending a message that does not require the extended capabilities, it SHOULD send the message whether or not the server announces support for the extension. 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.
如果支持UTF8SMTP的客户端正在发送不需要扩展功能的消息，则无论服务器是否宣布支持扩展，它都应发送该消息。换句话说，信封中的地址和消息的整个标题集都完全是ASCII格式的（可能包括标题中的编码字）。在这种情况下，无论服务器是否宣布此处指定的功能，客户端都应该发送消息。
In addition to the in-transit downgrades discussed above, downgrading may also occur before or during the initial message submission or after the 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.
除了上面讨论的传输中降级之外，降级也可能发生在初始邮件提交之前或期间，或者在传递到最终传递MTA之后。由于这些案例的可用信息与在途案例不同，因此约束条件和机会也可能有所不同。下面的小节将讨论这两种情况。
Perhaps obviously, the most convenient time to find an ASCII address corresponding to an internationalized address is at the originating MUA. This can occur either before the message is sent or after the internationalized form of the message is rejected. It is also the most convenient time to convert a message from the internationalized form into conventional ASCII form or to generate a non-delivery message to the sender if either is necessary. 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
很明显，查找与国际化地址对应的ASCII地址最方便的时间是在原始MUA。这可能发生在消息发送之前或消息的国际化形式被拒绝之后。这也是将消息从国际化格式转换为常规ASCII格式或在必要时生成未送达消息给发送方的最方便的时间。在这一点上，用户有一个完整的选择范围，包括联系带外的预期收件人以获得备用地址，咨询
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 of a user of at least moderate intelligence who wishes to communicate with another such user.
适当的目录，安排将地址和消息内容翻译成不同的语言，等等。虽然将消息降级视为最佳的全自动过程是很自然的，但我们不应低估希望与另一个此类用户通信的至少具有中等智能的用户的能力。
In this context, one can easily imagine modifications to message submission servers (as described in [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.
在这种情况下，可以很容易地想象对消息提交服务器（如[RFC4409]中所述）的修改，以便它们执行降级，甚至升级操作，接收带有此处讨论的一个或多个国际化扩展的消息，并根据需要调整传出消息，响应它遇到的传递或下一跳环境。
When an email message is received by a final delivery SMTP server, it is usually stored in some form. Then it is retrieved either by software that reads the stored form directly or by client software via some email retrieval mechanisms such as POP or IMAP.
当最终传递SMTP服务器收到电子邮件时，它通常以某种形式存储。然后通过直接读取存储表单的软件或通过一些电子邮件检索机制（如POP或IMAP）由客户端软件检索。
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.
第4.1节中描述的SMTP扩展仅在传输中提供保护。它不会阻止尚未升级以理解国际化地址和UTF-8头的MUA和电子邮件检索机制访问存储的国际化电子邮件。
Since the final delivery SMTP server (or, to be more specific, its corresponding mail storage agent) cannot safely assume that agents accessing email storage will 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 done, the final delivery SMTP server SHOULD include a mechanism to preserve or recover the original internationalized forms without information loss to support access by UTF8SMTP-aware agents.
由于最终传递SMTP服务器（或更具体地说，其相应的邮件存储代理）无法安全地假定访问电子邮件存储的代理始终能够处理此处建议的扩展，因此它可能会降级国际化电子邮件或专门识别使用这些扩展的邮件，或两者兼而有之。如果完成此操作，最终传递SMTP服务器应包括一种机制，用于在不丢失信息的情况下保留或恢复原始国际化表单，以支持UTF8SMTP感知代理的访问。
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.
本节确定了本规范集未涵盖但需要作为电子邮件地址和标头国际化部署一部分考虑的问题。
The mailto: schema defined in [RFC2368] and discussed in the Internationalized Resource Identifier (IRI) specification [RFC3987] may need to be modified when this work is completed and standardized.
[RFC2368]中定义并在国际化资源标识符（IRI）规范[RFC3987]中讨论的mailto:schema可能需要在该工作完成并标准化后进行修改。
The advent of UTF8SMTP will make necessary consideration of the interaction with delivery notification mechanisms, including the SMTP extension for requesting delivery notifications [RFC3461], and the format of delivery notifications [RFC3464]. These issues are discussed in a forthcoming document that will update those RFCs as needed [EAI-DSN].
UTF8SMTP的出现将对与传递通知机制的交互进行必要的考虑，包括用于请求传递通知的SMTP扩展[RFC3461]和传递通知的格式[RFC3464]。这些问题将在即将发布的文件中讨论，该文件将根据需要更新这些RFC[EAI-DSN]。
There are a number of places in contemporary Internet usage in which email addresses are used as identifiers for individuals, including as identifiers to Web servers supporting some electronic commerce sites. These documents do not address those uses, but it is reasonable to expect that some difficulties will be encountered when internationalized addresses are first used in those contexts, many of which cannot even handle the full range of addresses permitted today.
在当今互联网使用的许多地方，电子邮件地址被用作个人的标识符，包括作为支持某些电子商务网站的Web服务器的标识符。这些文件并未涉及这些用途，但可以合理预期，当国际化地址首次在这些环境中使用时，会遇到一些困难，其中许多甚至无法处理今天允许的全部地址范围。
One particular characteristic of the email format is its persistency: MUAs are expected to handle messages that were originally sent decades ago and not just those delivered seconds ago. As such, MUAs and mail filtering software, such as that specified in Sieve [RFC3028], will need to continue to accept and decode header fields that use the "encoded word" mechanism [RFC2047] to accommodate non-ASCII characters in some header fields. While extensions to both POP3 and IMAP have been proposed to enable automatic EAI-upgrade -- including RFC 2047 decoding -- of messages by the POP3 or IMAP server, there are message structures and MIME content-types for which that cannot be done or where the change would have unacceptable side effects.
电子邮件格式的一个特殊特征是它的持久性：MUA被期望处理几十年前最初发送的消息，而不仅仅是几秒钟前发送的消息。因此，MUA和邮件过滤软件（如筛[RFC3028]中指定的）将需要继续接受和解码使用“编码字”机制[RFC2047]的标题字段，以在某些标题字段中容纳非ASCII字符。虽然已经提出了对POP3和IMAP的扩展，以支持POP3或IMAP服务器对消息进行自动EAI升级（包括RFC 2047解码），但仍存在无法完成的消息结构和MIME内容类型，或者更改会产生不可接受的副作用。
For example, message parts that are cryptographically signed, using e.g., S/MIME [RFC3851] or Pretty Good Privacy (PGP) [RFC3156], cannot be upgraded from the RFC 2047 form to normal UTF-8 characters without breaking the signature. Similarly, message parts that are encrypted may contain, when decrypted, header fields that use the RFC 2047 encoding; such messages cannot be 'fully' upgraded without access to cryptographic keys.
例如，使用S/MIME[RFC3851]或Pretty Good Privacy（PGP）[RFC3156]等加密签名的消息部分无法在不破坏签名的情况下从RFC 2047表单升级为正常UTF-8字符。类似地，加密的消息部分在解密时可包含使用RFC 2047编码的报头字段；如果不访问加密密钥，则无法“完全”升级此类消息。
Similar issues may arise if signed messages are downgraded in transit [EAI-downgrade] and then an attempt is made to upgrade them to the original form and then verify the signatures. Even the very subtle changes that may result from algorithms to downgrade and then upgrade again may be sufficient to invalidate the signatures if they impact
如果签名消息在传输过程中降级[EAI降级]，然后尝试将其升级为原始格式，然后验证签名，则可能会出现类似问题。即使是由于算法降级然后再次升级而导致的非常细微的变化，如果它们影响了性能，也足以使签名失效
either the primary or MIME bodypart headers. When signatures are present, downgrading must be performed with extreme care if at all.
主标题或MIME bodypart标题。如果存在签名，则必须非常小心地进行降级。
Local parts are sometimes used to construct domain labels, e.g., the local part "user" in the address user@domain.example could be converted into a vanity host user.domain.example with its Web space at <http://user.domain.example> and the catchall addresses any.thing.goes@user.domain.example.
本地部分有时用于构造域标签，例如地址中的本地部分“用户”user@domain.example可以转换为虚拟主机user.domain.example，其Web空间位于<http://user.domain.example>catchall解决了任何问题。goes@user.domain.example.
Such schemes are obviously limited by, among other things, the SMTP rules for domain names, and will not work without further restrictions for other local parts such as the <utf8-local-part> specified in [EAI-UTF8]. Whether this issue is relevant to these specifications is an open question. It may be simply another case of the considerable flexibility accorded to delivery MTAs in determining the mailbox names they will accept and how they are interpreted.
除其他外，此类方案显然受到域名SMTP规则的限制，如果没有对其他本地部分（如[EAI-utf8]中指定的<utf8 local part>）的进一步限制，这些方案将无法工作。这个问题是否与这些规范相关是一个悬而未决的问题。这可能只是传递MTA在确定他们将接受的邮箱名称以及如何解释这些名称时具有相当大的灵活性的另一个例子。
Some applications use formats similar to the application/mbox format defined in [RFC4155] instead of the message/digest RFC 2046, Section 5.1.5 [RFC2046] form to transfer multiple messages as single units. Insofar as such applications assume that all stored messages use the message/rfc822 RFC 2046, Section 5.2.1 [RFC2046] format with US-ASCII headers, they are not ready for the extensions specified in this series of documents and special measures may be needed to properly detect and process them.
一些应用程序使用与[RFC4155]中定义的应用程序/mbox格式类似的格式，而不是第5.1.5节[RFC2046]表单中的消息/摘要RFC 2046，将多条消息作为单个单元传输。如果此类应用程序假定所有存储的消息都使用带有US-ASCII头的message/rfc822 RFC 2046第5.2.1节[RFC2046]格式，则这些应用程序尚未准备好进行本系列文档中指定的扩展，可能需要采取特殊措施来正确检测和处理这些消息。
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.
除了一个简单的问题外，这里概述的模型是否能够以令人满意的方式用于升级系统，并为未升级的系统提供足够的保护，我们预计，实际使用这些系统将为另外两个问题提供答案：应该对允许在地址局部使用的字符设置哪些限制，如字符列表或规范化，以及在实践中有多大用处，降级最终会受到任何必须施加的限制和约束。
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.
本概述说明和框架文件不考虑任何IANA注册或其他行动。小组中的一些文件有自己的IANA注意事项章节和要求。
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 the proposed fix involving forcing all displayed elements into normalized lower-case works for domain names in URLs, but not email local parts since those are case sensitive.
电子邮件地址中允许的字符和编码形式的任何扩展都会带来一些风险。关于所谓的“IDN欺骗”或“IDN同音词攻击”已经有过讨论。这些攻击允许攻击者（或“网络钓鱼者”）欺骗企业的域或URL。在国际化电子邮件地址的本地部分也可能发生同样的攻击。应该注意的是，建议的修复方法涉及强制所有显示的元素使用标准化的小写字母，但不适用于URL中的域名，因为它们是区分大小写的。
Since email addresses are often transcribed from business cards and notes on paper, they are subject to problems arising from confusable characters (see [RFC4690]). 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.
由于电子邮件地址通常是从纸面名片和便笺中转录而来的，因此容易因易混淆字符而出现问题（请参见[RFC4690]）。如果与邮箱关联的域是明确的，并且支持名称遵循本地系统约定的邮箱数量相对较少，则这些问题会有所减少。他们增加了非常大的邮件系统，用户可以自由选择自己的地址。
The internationalization of email addresses and headers must not leave the Internet less secure than it is without the required extensions. The requirements and mechanisms documented in this set 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 (see, e.g., [RFC4690]) -- and, potentially, some issues with UTF-8 normalization, discussed in [RFC3629], and other transformations. Normalization and other issues associated with transformations and standard forms are also part of the subject of ongoing work discussed in [Net-Unicode], in [IDNAbis-BIDI] and elsewhere. Some issues specifically related to internationalized addresses and headers 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.
电子邮件地址和邮件头的国际化不能使互联网的安全性低于没有所需扩展的情况。这组规范中记录的需求和机制通常不会引起任何新的安全问题。它们确实需要审查与可混淆字符相关的问题——这是一个在其他地方正在深入探讨的主题（参见，例如，[RFC4690]）——以及[RFC3629]中讨论的UTF-8规范化的一些潜在问题和其他转换。规范化和其他与转换和标准表单相关的问题也是[Net Unicode]、[IDNAbis BIDI]和其他地方正在进行的工作主题的一部分。本集中的其他文档将更详细地讨论与国际化地址和标题相关的一些问题。但是，特别要注意的是，任何“降级”机制或使用降级地址都不会不适当地假定国际化地址和ASCII地址之间存在经过身份验证的绑定。
The new UTF-8 header and message formats might also raise, or aggravate, another known issue. If the model creates new forms of an 'invalid' or 'malformed' message, then a new email attack is created: in an effort to be robust, some or most agents will accept such message and interpret them as if they were well-formed. If a filter interprets such a message differently than the final MUA, then it may be possible to create a message that appears acceptable under the filter's interpretation but should be rejected under the interpretation given to it by the final MUA. Such attacks already exist for existing messages and encoding layers, e.g., invalid MIME
新的UTF-8报头和消息格式也可能引发或加剧另一个已知问题。如果模型创建了新形式的“无效”或“格式错误”消息，则会创建新的电子邮件攻击：为了保持健壮性，一些或大多数代理会接受此类消息，并将其解释为格式正确。如果过滤器对此类消息的解释不同于最终MUA，则可能会创建一条在过滤器解释下可接受但在最终MUA给出的解释下应被拒绝的消息。现有消息和编码层已经存在此类攻击，例如无效MIME
syntax, invalid HTML markup, and invalid coding of particular image types.
语法、无效的HTML标记和特定图像类型的无效编码。
Models for the "downgrading" of messages or addresses from UTF-8 form to some ASCII form, including those described in [EAI-downgrade], pose another special problem and risk. Any system that transforms one address or set of mail header fields into another becomes a point at which spoofing attacks can occur and those who wish to spoof messages might be able to do so by imitating a message downgraded from one with a legitimate original address.
将消息或地址从UTF-8格式“降级”为某种ASCII格式的模型，包括[EAI降级]中所述的模型，带来了另一个特殊问题和风险。任何将一个地址或一组邮件头字段转换为另一个地址或一组邮件头字段的系统都会成为可能发生欺骗攻击的点，而那些希望欺骗邮件的人可以通过模仿从一个具有合法原始地址的系统降级的邮件来实现这一点。
In addition, email addresses are used in many contexts other than sending mail, such as for identifiers under various circumstances (see Section 6.3). 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.
此外，电子邮件地址用于除发送邮件以外的许多上下文，例如用于各种情况下的标识符（见第6.3节）。这些上下文中的每一个都需要依次进行评估，以确定使用非ASCII格式是否合适，以及它们会引起哪些特殊问题。
This work will clearly impact any systems or mechanisms that are dependent on digital signatures or similar integrity protection for mail headers (see also the discussion in Section 6.4). Many 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 on domain keys identified mail (DKIM [DKIM-Charter]) 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 if the two sets of protocols are to co-exist. In addition, to the degree to which email addresses appear in PKI (Public Key Infrastructure) certificates, standards addressing such certificates will need to be upgraded to address these internationalized addresses. Those upgrades will need to address questions of spoofing by look-alikes of the addresses themselves.
这项工作显然会影响任何依赖于数字签名或类似邮件头完整性保护的系统或机制（另请参见第6.4节中的讨论）。PGP和S/MIME的许多常规用法不受影响，因为它们用于对正文部分进行签名，而不是对标题进行签名。另一方面，域密钥识别邮件（DKIM[DKIM宪章]）的开发工作最终将需要考虑这项工作，反之亦然：虽然本实验不建议解决或解决由DKIM和其他签名头机制提出的问题，如果这两套协议要共存，这些问题最终必须得到协调和解决。此外，根据电子邮件地址在PKI（公钥基础设施）证书中出现的程度，需要升级处理此类证书的标准，以处理这些国际化地址。这些升级需要解决通过地址本身的相似性进行欺骗的问题。
This document, and the related ones, were originally derived from documents 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 document by Paul Hoffman and Adam Costello [Hoffman-IMAA] that attempted to define an MUA-only solution to the address internationalization problem.
本文件及相关文件最初来源于John Klensin和JET集团[Klensin emailaddr]，[JET-IMA]的文件。这项工作的灵感来自互联网邮件联盟赞助的“IMAA”邮件列表讨论，特别是保罗·霍夫曼（Paul Hoffman）和亚当·科斯特洛（Adam Costello）[Hoffman IMAA]的早期文件，该文件试图为地址国际化问题定义一个只有MUA的解决方案。
More recent documents have benefited from considerable discussion within the IETF EAI Working Group and especially from suggestions and text provided by Martin Duerst, Frank Ellermann, Philip Guenther, Kari Hurtta, and Alexey Melnikov, and from extended discussions among
最近的文件得益于IETF EAI工作组内的大量讨论，特别是Martin Duerst、Frank Ellermann、Philip Guenther、Kari Hurtta和Alexey Melnikov提供的建议和文本，以及IETF EAI工作组之间的广泛讨论
the editors and authors of the core documents cited in Section 3: Harald Alvestrand, Kazunori Fujiwara, Chris Newman, Pete Resnick, Jiankang Yao, Jeff Yeh, and Yoshiro Yoneya.
第3节引用的核心文件的编辑和作者：Harald Alvestrand、Kazunori Fujiwara、Chris Newman、Pete Resnick、姚建康、Jeff Yeh和Yoseya Yoshiro。
Additional comments received during IETF Last Call, including those from Paul Hoffman and Robert Sparks, were helpful in making the document more clear and comprehensive.
IETF上次通话期间收到的其他评论，包括保罗·霍夫曼（Paul Hoffman）和罗伯特·斯帕克斯（Robert Sparks）的评论，有助于使文件更加清晰和全面。
[ASCII] American National Standards Institute (formerly United States of America Standards Institute), "USA Code for Information Interchange", ANSI X3.4-1968, 1968.
[ASCII]美国国家标准协会（前美国标准协会），“美国信息交换代码”，ANSI X3.4-1968，1968年。
ANSI X3.4-1968 has been replaced by newer versions with slight modifications, but the 1968 version remains definitive for the Internet.
ANSI X3.4-1968已被稍作修改的较新版本所取代，但1968年版本仍然是互联网的最终版本。
[RFC1652] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D. Crocker, "SMTP Service Extension for 8bit-MIMEtransport", RFC 1652, July 1994.
[RFC1652]Klensin，J.，Freed，N.，Rose，M.，Stefferud，E.，和D.Crocker，“8bit MIMEtransport的SMTP服务扩展”，RFC 16521994年7月。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels'", RFC 2119, BCP 14, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，RFC 2119，BCP 14，1997年3月。
[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April 2001.
[RFC2821]Klensin，J.，“简单邮件传输协议”，RFC 28212001年4月。
[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing Domain Names in Applications (IDNA)", RFC 3490, March 2003.
[RFC3490]Faltstrom，P.，Hoffman，P.，和A.Costello，“应用程序中的域名国际化（IDNA）”，RFC 34902003年3月。
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003.
[RFC3629]Yergeau，F.，“UTF-8，ISO 10646的转换格式”，STD 63，RFC 3629，2003年11月。
[DKIM-Charter] IETF, "Domain Keys Identified Mail (dkim)", October 2006, <http://www.ietf.org/ html.charters/dkim-charter.html>.
[DKIM章程]IETF，“域密钥识别邮件（DKIM）”，2006年10月<http://www.ietf.org/ html.charters/dkim charter.html>。
[EAI-DSN] Newman, C., "UTF-8 Delivery and Disposition Notification", Work in Progress, January 2007.
[EAI-DSN]Newman，C.，“UTF-8交付和处置通知”，在建工程，2007年1月。
[EAI-SMTPext] Yao, J., Ed. and W. Mao, Ed., "SMTP extension for internationalized email address", Work in Progress, June 2007.
[EAI SMTPext]Yao，J.，Ed.和W.Mao，Ed.，“国际化电子邮件地址的SMTP扩展”，正在进行的工作，2007年6月。
[EAI-UTF8] Yeh, J., "Internationalized Email Headers", Work in Progress, April 2007.
[EAI-UTF8]Yeh，J.，“国际化电子邮件标题”，正在进行的工作，2007年4月。
[EAI-downgrade] Yoneya, Y., Ed. and K. Fujiwara, Ed., "Downgrading mechanism for Internationalized eMail Address (IMA)", Work in Progress, March 2007.
[EAI降级]Yoneya，Y.，Ed.和K.Fujiwara，Ed.，“国际化电子邮件地址（IMA）降级机制”，正在进行的工作，2007年3月。
[EAI-imap] Resnick, P. and C. Newman, "IMAP Support for UTF-8", Work in Progress, March 2007.
[EAI imap]Resnick，P.和C.Newman，“对UTF-8的imap支持”，正在进行的工作，2007年3月。
[EAI-pop] Newman, C., "POP3 Support for UTF-8", Work in Progress, January 2007.
[EAI pop]Newman，C.，“对UTF-8的POP3支持”，正在进行的工作，2007年1月。
[EAI-scenarios] Alvestrand, H., "UTF-8 Mail: Scenarios", Work in Progress, February 2007.
[EAI场景]Alvestrand，H.，“UTF-8邮件：场景”，正在进行的工作，2007年2月。
[Hoffman-IMAA] Hoffman, P. and A. Costello, "Internationalizing Mail Addresses in Applications (IMAA)", Work in Progress, October 2003.
[Hoffman IMAA]Hoffman，P.和A.Costello，“应用程序中的邮件地址国际化（IMAA）”，正在进行的工作，2003年10月。
[IDNAbis-BIDI] Alvestrand, H. and C. Karp, "An IDNA problem in right-to-left scripts", Work in Progress, October 2006.
[IDNAbis BIDI]Alvestrand，H.和C.Karp，“从右到左脚本中的IDNA问题”，正在进行的工作，2006年10月。
[JET-IMA] Yao, J. and J. Yeh, "Internationalized eMail Address (IMA)", Work in Progress, June 2005.
[JET-IMA]Yao，J.和Yeh，“国际化电子邮件地址（IMA）”，正在进行的工作，2005年6月。
[Klensin-emailaddr] Klensin, J., "Internationalization of Email Addresses", Work in Progress, July 2005.
[Klensin emailaddr]Klensin，J.，“电子邮件地址的国际化”，正在进行的工作，2005年7月。
[Net-Unicode] Klensin, J. and M. Padlipsky, "Unicode Format for Network Interchange", Work in Progress, March 2007.
[Net Unicode]Klensin，J.和M.Padlipsky，“网络交换的Unicode格式”，正在进行的工作，2007年3月。
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.
[RFC2045]Freed，N.和N.Borenstein，“多用途Internet邮件扩展（MIME）第一部分：Internet邮件正文格式”，RFC 20451996年11月。
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996.
[RFC2046]Freed，N.和N.Borenstein，“多用途Internet邮件扩展（MIME）第二部分：媒体类型”，RFC 20461996年11月。
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text", RFC 2047, November 1996.
[RFC2047]Moore，K.，“MIME（多用途互联网邮件扩展）第三部分：非ASCII文本的消息头扩展”，RFC 2047，1996年11月。
[RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations", RFC 2231, November 1997.
[RFC2231]Freed，N.和K.Moore，“MIME参数值和编码字扩展：字符集、语言和连续体”，RFC 22311997年11月。
[RFC2368] Hoffman, P., Masinter, L., and J. Zawinski, "The mailto URL scheme", RFC 2368, July 1998.
[RFC2368]Hoffman，P.，Masinter，L.，和J.Zawinski，“邮件URL方案”，RFC 2368，1998年7月。
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April 2001.
[RFC2822]Resnick，P.，“互联网信息格式”，RFC 2822，2001年4月。
[RFC3028] Showalter, T., "Sieve: A Mail Filtering Language", RFC 3028, January 2001.
[RFC3028]Showalter，T.，“筛选：邮件过滤语言”，RFC3028，2001年1月。
[RFC3156] Elkins, M., Del Torto, D., Levien, R., and T. Roessler, "MIME Security with OpenPGP", RFC 3156, August 2001.
[RFC3156]Elkins，M.，Del Torto，D.，Levien，R.，和T.Roessler，“OpenPGP的MIME安全性”，RFC 3156，2001年8月。
[RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs)", RFC 3461, January 2003.
[RFC3461]Moore，K.，“用于传递状态通知（DSN）的简单邮件传输协议（SMTP）服务扩展”，RFC 3461，2003年1月。
[RFC3464] Moore, K. and G. Vaudreuil, "An Extensible Message Format for Delivery Status Notifications", RFC 3464, January 2003.
[RFC3464]Moore，K.和G.Vaudreuil，“交付状态通知的可扩展消息格式”，RFC 3464，2003年1月。
[RFC3851] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification", RFC 3851, July 2004.
[RFC3851]Ramsdell，B.，“安全/多用途Internet邮件扩展（S/MIME）版本3.1消息规范”，RFC 38512004年7月。
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, January 2005.
[RFC3987]Duerst，M.和M.Suignard，“国际化资源标识符（IRIs）”，RFC 3987，2005年1月。
[RFC4155] Hall, E., "The application/mbox Media Type", RFC 4155, September 2005.
[RFC4155]Hall，E.“应用程序/mbox媒体类型”，RFC 4155，2005年9月。
[RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail", RFC 4409, April 2006.
[RFC4409]Gellens，R.和J.Klensin，“邮件邮件提交”，RFC 4409，2006年4月。
[RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and Recommendations for Internationalized Domain Names (IDNs)", RFC 4690, September 2006.
[RFC4690]Klensin，J.，Faltstrom，P.，Karp，C.，和IAB，“国际化域名（IDN）的审查和建议”，RFC 46902006年9月。
Authors' Addresses
作者地址
John C Klensin 1770 Massachusetts Ave, #322 Cambridge, MA 02140 USA
美国马萨诸塞州剑桥市322号马萨诸塞大道1770号约翰·C·克伦辛，邮编：02140
Phone: +1 617 491 5735
EMail: john-ietf@jck.com
Phone: +1 617 491 5735
EMail: john-ietf@jck.com
YangWoo Ko ICU 119 Munjiro Yuseong-gu, Daejeon 305-732 Republic of Korea
大韩民国大田市阳湖ICU 119 Munjiro Yuseong gu 305-732
EMail: yw@mrko.pe.kr
EMail: yw@mrko.pe.kr
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