Network Working Group D. Crocker
Request for Comments: 5598 Brandenburg InternetWorking
Category: Informational July 2009
Network Working Group D. Crocker
Request for Comments: 5598 Brandenburg InternetWorking
Category: Informational July 2009
Internet Mail Architecture
Internet邮件体系结构
Abstract
摘要
Over its thirty-five-year history, Internet Mail has changed significantly in scale and complexity, as it has become a global infrastructure service. These changes have been evolutionary, rather than revolutionary, reflecting a strong desire to preserve both its installed base and its usefulness. To collaborate productively on this large and complex system, all participants need to work from a common view of it and use a common language to describe its components and the interactions among them. But the many differences in perspective currently make it difficult to know exactly what another participant means. To serve as the necessary common frame of reference, this document describes the enhanced Internet Mail architecture, reflecting the current service.
在其35年的历史中，互联网邮件在规模和复杂性方面发生了重大变化，因为它已成为一种全球基础设施服务。这些变化是渐进式的，而不是革命性的，反映出人们强烈希望保留其安装基础和用途。为了在这个庞大而复杂的系统上进行有效的合作，所有参与者都需要从一个共同的角度来看待它，并使用一种共同的语言来描述它的组件以及它们之间的交互。但是，目前观点上的许多差异使得我们很难确切地知道另一位参与者的意思。为了作为必要的通用参考框架，本文档描述了增强的Internet邮件体系结构，反映了当前的服务。
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) 2009 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2009 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document.
本文件受BCP 78和IETF信托在本文件出版之日生效的与IETF文件有关的法律规定的约束(http://trustee.ietf.org/license-info). 请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。
This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may
本文件可能包含2008年11月10日之前发布或公开的IETF文件或IETF贡献中的材料。控制某些材料版权的人员可能未授予IETF信托允许在IETF标准流程之外修改此类材料的权利。在未从控制此类材料版权的人员处获得充分许可的情况下，不得在IETF标准流程之外修改本文件，其衍生作品可能会
not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.
不得在IETF标准流程之外创建，除非将其格式化以RFC形式发布，或将其翻译成英语以外的语言。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. History . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. The Role of This Architecture . . . . . . . . . . . . . . 6
1.3. Document Conventions . . . . . . . . . . . . . . . . . . . 7
2. Responsible Actor Roles . . . . . . . . . . . . . . . . . . . 7
2.1. User Actors . . . . . . . . . . . . . . . . . . . . . . . 8
2.2. Message Handling Service (MHS) Actors . . . . . . . . . . 11
2.3. Administrative Actors . . . . . . . . . . . . . . . . . . 14
3. Identities . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1. Mailbox . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2. Scope of Email Address Use . . . . . . . . . . . . . . . . 18
3.3. Domain Names . . . . . . . . . . . . . . . . . . . . . . . 19
3.4. Message Identifier . . . . . . . . . . . . . . . . . . . . 19
4. Services and Standards . . . . . . . . . . . . . . . . . . . . 21
4.1. Message Data . . . . . . . . . . . . . . . . . . . . . . . 24
4.1.4. Identity References in a Message . . . . . . . . . . . 25
4.2. User-Level Services . . . . . . . . . . . . . . . . . . . 29
4.3. MHS-Level Services . . . . . . . . . . . . . . . . . . . . 31
4.4. Transition Modes . . . . . . . . . . . . . . . . . . . . . 34
4.5. Implementation and Operation . . . . . . . . . . . . . . . 35
5. Mediators . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.1. Alias . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.2. ReSender . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.3. Mailing Lists . . . . . . . . . . . . . . . . . . . . . . 39
5.4. Gateways . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.5. Boundary Filter . . . . . . . . . . . . . . . . . . . . . 42
6. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 42
6.1. Security Considerations . . . . . . . . . . . . . . . . . 42
6.2. Internationalization . . . . . . . . . . . . . . . . . . . 43
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 45
7.1. Normative References . . . . . . . . . . . . . . . . . . . 45
7.2. Informative References . . . . . . . . . . . . . . . . . . 47
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 50
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. History . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. The Role of This Architecture . . . . . . . . . . . . . . 6
1.3. Document Conventions . . . . . . . . . . . . . . . . . . . 7
2. Responsible Actor Roles . . . . . . . . . . . . . . . . . . . 7
2.1. User Actors . . . . . . . . . . . . . . . . . . . . . . . 8
2.2. Message Handling Service (MHS) Actors . . . . . . . . . . 11
2.3. Administrative Actors . . . . . . . . . . . . . . . . . . 14
3. Identities . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1. Mailbox . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2. Scope of Email Address Use . . . . . . . . . . . . . . . . 18
3.3. Domain Names . . . . . . . . . . . . . . . . . . . . . . . 19
3.4. Message Identifier . . . . . . . . . . . . . . . . . . . . 19
4. Services and Standards . . . . . . . . . . . . . . . . . . . . 21
4.1. Message Data . . . . . . . . . . . . . . . . . . . . . . . 24
4.1.4. Identity References in a Message . . . . . . . . . . . 25
4.2. User-Level Services . . . . . . . . . . . . . . . . . . . 29
4.3. MHS-Level Services . . . . . . . . . . . . . . . . . . . . 31
4.4. Transition Modes . . . . . . . . . . . . . . . . . . . . . 34
4.5. Implementation and Operation . . . . . . . . . . . . . . . 35
5. Mediators . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.1. Alias . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.2. ReSender . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.3. Mailing Lists . . . . . . . . . . . . . . . . . . . . . . 39
5.4. Gateways . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.5. Boundary Filter . . . . . . . . . . . . . . . . . . . . . 42
6. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 42
6.1. Security Considerations . . . . . . . . . . . . . . . . . 42
6.2. Internationalization . . . . . . . . . . . . . . . . . . . 43
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 45
7.1. Normative References . . . . . . . . . . . . . . . . . . . 45
7.2. Informative References . . . . . . . . . . . . . . . . . . 47
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 50
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Over its thirty-five-year history, Internet Mail has changed significantly in scale and complexity, as it has become a global infrastructure service. These changes have been evolutionary, rather than revolutionary, reflecting a strong desire to preserve both its installed base and its usefulness. Today, Internet Mail is distinguished by many independent operators, many different components for providing service to Users, as well as many different components that transfer messages.
在其35年的历史中，互联网邮件在规模和复杂性方面发生了重大变化，因为它已成为一种全球基础设施服务。这些变化是渐进式的，而不是革命性的，反映出人们强烈希望保留其安装基础和用途。今天，Internet Mail的显著特点是有许多独立的运营商、为用户提供服务的许多不同组件以及传递消息的许多不同组件。
The underlying technical standards for Internet Mail comprise a rich array of functional capabilities. These specifications form the core:
Internet邮件的底层技术标准包含丰富的功能性功能。这些规范构成了核心：
* Simple Mail Transfer Protocol (SMTP) ([RFC0821], [RFC2821], [RFC5321]) moves a message through the Internet.
* 简单邮件传输协议（SMTP）（[RFC0821]、[RFC2821]、[RFC5321]）通过Internet移动邮件。
* Internet Mail Format (IMF) ([RFC0733], [RFC0822], [RFC2822], [RFC5322]) defines a message object.
* Internet邮件格式（IMF）（[RFC0733]、[RFC0822]、[RFC2822]、[RFC5322]）定义消息对象。
* Multipurpose Internet Mail Extensions (MIME) [RFC2045] defines an enhancement to the message object that permits using multimedia attachments.
* 多用途Internet邮件扩展（MIME）[RFC2045]定义了对消息对象的增强，允许使用多媒体附件。
Public collaboration on technical, operations, and policy activities of email, including those that respond to the challenges of email abuse, has brought a much wider range of participants into the technical community. To collaborate productively on this large and complex system, all participants need to work from a common view of it and use a common language to describe its components and the interactions among them. But the many differences in perspective currently make it difficult to know exactly what another participant means.
在电子邮件的技术、操作和政策活动方面的公共合作，包括应对电子邮件滥用挑战的活动，已经将更广泛的参与者带入了技术界。为了在这个庞大而复杂的系统上进行有效的合作，所有参与者都需要从一个共同的角度来看待它，并使用一种共同的语言来描述它的组件以及它们之间的交互。但是，目前观点上的许多差异使得我们很难确切地知道另一位参与者的意思。
It is the need to resolve these differences that motivates this document, which describes the realities of the current system. Internet Mail is the subject of ongoing technical, operations, and policy work, and the discussions often are hindered by different models of email-service design and different meanings for the same terms.
正是解决这些分歧的需要推动了本文件，该文件描述了当前制度的现实情况。互联网邮件是正在进行的技术、运营和政策工作的主题，讨论往往受到电子邮件服务设计的不同模式和相同术语的不同含义的阻碍。
To serve as the necessary common frame of reference, this document describes the enhanced Internet Mail architecture, reflecting the current service. The document focuses on:
为了作为必要的通用参考框架，本文档描述了增强的Internet邮件体系结构，反映了当前的服务。该文件的重点是：
* Capturing refinements to the email model
* 捕获对电子邮件模型的改进
* Clarifying functional roles for the architectural components
* 明确体系结构组件的功能角色
* Clarifying identity-related issues, across the email service
* 通过电子邮件服务澄清与身份相关的问题
* Defining terminology for architectural components and their interactions
* 定义架构组件及其交互的术语
The first standardized architecture for networked email specified a simple split between the user world, in the form of Message User Agents (MUAs), and the transfer world, in the form of the Message Handling Service (MHS), which is composed of Message Transfer Agents (MTAs) [RFC1506]. The MHS accepts a message from one User and delivers it to one or more other Users, creating a virtual MUA-to-MUA exchange environment.
网络电子邮件的第一个标准化体系结构规定了用户世界（以消息用户代理（MUA）的形式）和传输世界（以消息处理服务（MHS）的形式）之间的简单划分，后者由消息传输代理（MTA）组成[RFC1506]。MHS接受来自一个用户的消息并将其传递给一个或多个其他用户，从而创建一个虚拟的MUA到MUA交换环境。
As shown in Figure 1, this architecture defines two logical layers of interoperability. One is directly between Users. The other is among the components along the transfer path. In addition, there is interoperability between the layers, first when a message is posted from the User to the MHS and later when it is delivered from the MHS to the User.
如图1所示，该体系结构定义了互操作性的两个逻辑层。一个是直接在用户之间。另一个是沿传输路径的组件之间。此外，各层之间存在互操作性，首先是当消息从用户发布到MHS时，然后是当消息从MHS传递到用户时。
The operational service has evolved, although core aspects of the service, such as mailbox addressing and message format style, remain remarkably constant. The original distinction between the user level and transfer level remains, but with elaborations in each. The term "Internet Mail" is used to refer to the entire collection of user and transfer components and services.
尽管服务的核心方面（如邮箱地址和消息格式样式）保持不变，但运营服务仍在不断发展。用户级和传输级之间的原始区别仍然存在，但在每个级别都有详细说明。术语“Internet邮件”用于指用户和传输组件及服务的整个集合。
For Internet Mail, the term "end-to-end" usually refers to a single posting and the set of deliveries that result from a single transit of the MHS. A common exception is group dialogue that is mediated through a Mailing List; in this case, two postings occur before intended Recipients receive an Author's message, as discussed in Section 2.1.4. In fact, some uses of email consider the entire email service, including Author and Recipient, as a subordinate component. For these services, "end-to-end" refers to points outside the email service. Examples are voicemail over email [RFC3801], EDI (Electronic Data Interchange) over email [RFC1767], and facsimile over email [RFC4142].
对于互联网邮件，术语“端到端”通常指一次投递以及MHS单次中转产生的一组投递。一个常见的例外是通过邮件列表进行的群组对话；在这种情况下，如第2.1.4节所述，在预期收件人收到作者的邮件之前会出现两次帖子。事实上，电子邮件的一些使用考虑了整个电子邮件服务，包括作者和接收者，作为从属组件。对于这些服务，“端到端”是指电子邮件服务之外的点。例如，通过电子邮件发送的语音邮件[RFC3801]、通过电子邮件发送的EDI（电子数据交换）[RFC1767]和通过电子邮件发送的传真[RFC4142]。
+--------+
++================>| User |
|| +--------+
|| ^
+--------+ || +--------+ .
| User +==++=========>| User | .
+---+----+ || +--------+ .
. || ^ .
. || +--------+ . .
. ++==>| User | . .
. +--------+ . .
. ^ . .
. . . .
V . . .
+---+-----------------+------+------+---+
| . . . . |
| .................>. . . |
| . . . |
| ........................>. . |
| . . |
| ...............................>. |
| |
| Message Handling Service (MHS) |
+---------------------------------------+
+--------+
++================>| User |
|| +--------+
|| ^
+--------+ || +--------+ .
| User +==++=========>| User | .
+---+----+ || +--------+ .
. || ^ .
. || +--------+ . .
. ++==>| User | . .
. +--------+ . .
. ^ . .
. . . .
V . . .
+---+-----------------+------+------+---+
| . . . . |
| .................>. . . |
| . . . |
| ........................>. . |
| . . |
| ...............................>. |
| |
| Message Handling Service (MHS) |
+---------------------------------------+
Legend: === lines indicate primary (possibly indirect) transfers or roles ... lines indicate supporting transfers or roles
图例：==行表示主要（可能是间接）传输或角色。。。行表示支持转移或角色
Figure 1: Basic Internet Mail Service Model
图1：基本Internet邮件服务模型
End-to-end Internet Mail exchange is accomplished by using a standardized infrastructure with these components and characteristics:
端到端Internet邮件交换通过使用具有以下组件和特征的标准化基础架构来实现：
* An email object
* 电子邮件对象
* Global addressing
* 全局寻址
* An asynchronous sequence of point-to-point transfer mechanisms
* 点到点传输机制的异步序列
* No requirement for prior arrangement between MTAs or between Authors and Recipients
* MTA之间或作者与收件人之间无需事先安排
* No requirement for prior arrangement between point-to-point transfer services over the open Internet
* 无需事先安排开放互联网上的点到点传输服务
* No requirement for Author, Originator, or Recipients to be online at the same time
* 不要求作者、发起者或接收者同时在线
The end-to-end portion of the service is the email object, called a "message". Broadly, the message itself distinguishes control information, for handling, from the Author's content.
服务的端到端部分是电子邮件对象，称为“消息”。一般来说，消息本身将用于处理的控制信息与作者的内容区分开来。
A precept to the design of mail over the open Internet is permitting User-to-User and MTA-to-MTA interoperability without prior, direct arrangement between the independent administrative authorities responsible for handling a message. All participants rely on having the core services universally supported and accessible, either directly or through Gateways that act as translators between Internet Mail and email environments conforming to other standards. Given the importance of spontaneity and serendipity in interpersonal communications, not requiring such prearrangement between participants is a core benefit of Internet Mail and remains a core requirement for it.
开放互联网上邮件设计的一个原则是允许用户对用户和MTA对MTA的互操作性，而无需事先在负责处理邮件的独立管理机构之间进行直接安排。所有参与者都依赖于核心服务得到普遍支持和访问，直接或通过网关作为符合其他标准的Internet邮件和电子邮件环境之间的翻译人员。考虑到自发性和偶然性在人际沟通中的重要性，不要求参与者之间进行事先安排是互联网邮件的核心优势，也是它的核心要求。
Within localized networks at the edge of the public Internet, prior administrative arrangement often is required and can include access control, routing constraints, and configuration of the information query service. Although Recipient authentication has usually been required for message access since the beginning of Internet Mail, in recent years it also has been required for message submission. In these cases, a server validates the client's identity, whether by explicit security protocols or by implicit infrastructure queries to identify "local" participants.
在公共互联网边缘的本地化网络中，通常需要事先进行管理安排，包括访问控制、路由约束和信息查询服务的配置。虽然自Internet邮件开始以来，邮件访问通常需要收件人身份验证，但近年来，邮件提交也需要收件人身份验证。在这些情况下，服务器验证客户机的身份，无论是通过显式安全协议还是通过隐式基础结构查询来识别“本地”参与者。
An Internet service is an integration of related capabilities among two or more participating nodes. The capabilities are accomplished across the Internet by one or more protocols. What connects a protocol to a service is an architecture. An architecture specifies how the protocols implement the service by defining the logical components of a service and the relationships among them. From that logical view, a service defines what is being done, an architecture defines where the pieces are (in relation to each other), and a protocol defines how particular capabilities are performed.
Internet服务是两个或多个参与节点之间相关功能的集成。这些功能通过一个或多个协议在Internet上实现。将协议连接到服务的是体系结构。体系结构通过定义服务的逻辑组件及其之间的关系来指定协议如何实现服务。从这个逻辑视图来看，服务定义正在做什么，体系结构定义各个部分的位置（相互之间的关系），协议定义如何执行特定功能。
As such, an architecture will more formally describe a service at a relatively high level. A protocol that implements some portion of a service will conform to the architecture to a greater or lesser extent, depending on the pragmatic tradeoffs they make when trying to implement the architecture in the context of real-world constraints. Failure to precisely follow an architecture is not a failure of the protocol, nor is failure to precisely cast a protocol a failure of
因此，体系结构将在相对较高的级别上更正式地描述服务。实现服务某一部分的协议将或多或少地符合体系结构，这取决于它们在实际约束环境中尝试实现体系结构时所做的实际权衡。未能准确遵循体系结构不是协议的失败，也不是协议的失败
the architecture. Where a protocol varies from the architecture, it will of course be appropriate for it to explain the reason for the variance. However, such variance is not a mark against a protocol: Happily, the IETF prefers running code to architectural purity.
建筑。当协议与体系结构不同时，它当然适合解释差异的原因。然而，这种差异并不是协议的标志：令人高兴的是，IETF更喜欢运行代码，而不是架构纯度。
In this particular case, this architecture attempts to define the logical components of Internet email and does so post hoc, trying to capture the architectural principles that the current email protocols embody. To different extents, email protocols will conform to this architecture more or less well. Insofar as this architecture differs from those protocols, the reasons are generally well understood and are required for interoperation. The differences are not a sign that protocols need to be fixed. However, this architecture is a best attempt at a logical model of Internet email, and insofar as new protocol development varies from this architecture, it is necessary for designers to understand those differences and explain them carefully.
在这种特殊情况下，该体系结构试图定义Internet电子邮件的逻辑组件，并在事后进行定义，试图捕获当前电子邮件协议所体现的体系结构原则。在不同程度上，电子邮件协议或多或少地符合这种体系结构。由于该体系结构不同于那些协议，因此一般都能很好地理解其中的原因，并且是互操作所必需的。这些差异并不是协议需要修复的迹象。然而，该体系结构是对Internet电子邮件逻辑模型的最佳尝试，并且由于新协议的开发与该体系结构不同，设计者有必要理解这些差异并仔细解释它们。
References to structured fields of a message use a two-part dotted notation. The first part cites the document that contains the specification for the field, and the second part is the name of the field. Hence <RFC5322.From> is the IMF From: header field in an email content header, and <RFC5321.MailFrom> is the address in the SMTP "Mail From" command.
对消息的结构化字段的引用使用由两部分组成的虚线表示法。第一部分引用了包含字段规范的文档，第二部分是字段的名称。因此，<RFC5322.From>是电子邮件内容标题中的IMF-From:header字段，<RFC5321.MailFrom>是SMTP“邮件发件人”命令中的地址。
When occurring without the IMF (RFC 5322) qualifier, header field names are shown with a colon suffix. For example, From:.
在没有IMF（RFC 5322）限定符的情况下出现时，标题字段名称将显示为冒号后缀。例如，From:。
References to labels for actors, functions or components have the first letter capitalized.
对参与者、函数或组件标签的引用的首字母大写。
Internet Mail is a highly distributed service, with a variety of Actors playing different roles. These Actors fall into three basic types:
Internet邮件是一种高度分布式的服务，各种参与者扮演着不同的角色。这些参与者分为三种基本类型：
* User
* 使用者
* Message Handling Service (MHS)
* 信息处理服务（MHS）
* ADministrative Management Domain (ADMD)
* 管理管理域（ADMD）
Although related to a technical architecture, the focus on Actors concerns participant responsibilities, rather than functionality of modules. For that reason, the labels used are different from those used in classic diagrams of email architecture.
尽管与技术架构相关，但对参与者的关注关注关注的是参与者的责任，而不是模块的功能。因此，使用的标签与电子邮件体系结构的经典图表中使用的标签不同。
Users are the sources and sinks of messages. Users can be people, organizations, or processes. They can have an exchange that iterates, and they can expand or contract the set of Users that participate in a set of exchanges. In Internet Mail, there are four types of Users:
用户是消息的源和汇。用户可以是人员、组织或流程。它们可以有一个迭代的交换，并且可以扩展或收缩参与一组交换的用户集。在Internet邮件中，有四种类型的用户：
* Authors
* 作者
* Recipients
* 接受者
* Return Handlers
* 返回处理程序
* Mediators
* 调解员
Figure 2 shows the primary and secondary flows of messages among them. As a pragmatic heuristic: User Actors can generate, modify, or look at the whole message.
图2显示了它们之间的主要和次要消息流。作为一种实用的启发：用户参与者可以生成、修改或查看整个消息。
++==========++
|| Author ||<..................................<..
++=++=++=++=++ .
|| || || ++===========++ .
|| || ++====>|| Recipient || .
|| || ++=====+=====++ .
|| || . .
|| || ..........................>.+
|| || .
|| || ................... .
|| || . . .
|| || V . .
|| || +-----------+ ++=====+=====++ .
|| ++========>| Mediator +===>|| Recipient || .
|| +-----+-----+ ++=====+=====++ .
|| . . .
|| ..................+.......>.+
|| .
|| ..............+.................. .
|| . . . .
\/ V V ' .
+-----------+ +-----------+ ++=====+=====++ .
| Mediator +===>| Mediator +===>|| Recipient || .
+-----+-----+ +-----+-----+ ++=====+=====++ .
. . . .
.................+.................+.......>..
++==========++
|| Author ||<..................................<..
++=++=++=++=++ .
|| || || ++===========++ .
|| || ++====>|| Recipient || .
|| || ++=====+=====++ .
|| || . .
|| || ..........................>.+
|| || .
|| || ................... .
|| || . . .
|| || V . .
|| || +-----------+ ++=====+=====++ .
|| ++========>| Mediator +===>|| Recipient || .
|| +-----+-----+ ++=====+=====++ .
|| . . .
|| ..................+.......>.+
|| .
|| ..............+.................. .
|| . . . .
\/ V V ' .
+-----------+ +-----------+ ++=====+=====++ .
| Mediator +===>| Mediator +===>|| Recipient || .
+-----+-----+ +-----+-----+ ++=====+=====++ .
. . . .
.................+.................+.......>..
Legend: === lines indicate primary (possibly indirect) transfers or roles ... lines indicate supporting transfers or roles
图例：==行表示主要（可能是间接）传输或角色。。。行表示支持转移或角色
Figure 2: Relationships among User Actors
图2：用户参与者之间的关系
From a User's perspective, all message-transfer activities are performed by a monolithic Message Handling Service (MHS), even though the actual service can be provided by many independent organizations. Users are customers of this unified service.
从用户的角度来看，所有的消息传输活动都由单一消息处理服务（MHS）执行，即使实际的服务可以由许多独立的组织提供。用户是此统一服务的客户。
Whenever any MHS Actor sends information back to an Author or Originator in the sequence of handling a message, that Actor is a User.
每当任何MHS参与者按照处理消息的顺序将信息发送回作者或发起人时，该参与者就是用户。
The Author is responsible for creating the message, its contents, and its list of Recipient addresses. The MHS transfers the message from the Author and delivers it to the Recipients. The MHS has an Originator role (Section 2.2.1) that correlates with the Author role.
作者负责创建邮件、邮件内容和收件人地址列表。MHS从作者处传输消息并将其传递给收件人。MHS具有与作者角色相关的发起人角色（第2.2.1节）。
The Recipient is a consumer of the delivered message. The MHS has a Receiver role (Section 2.2.4) that correlates with the Recipient role. This is labeled Recv in Figure 3.
收件人是已传递邮件的使用者。MHS具有与接收者角色相关的接收者角色（第2.2.4节）。这在图3中标记为Recv。
Any Recipient can close the user-communication loop by creating and submitting a new message that replies to the Author. An example of an automated form of reply is the Message Disposition Notification (MDN), which informs the Author about the Recipient's handling of the message. (See Section 4.1.)
任何收件人都可以通过创建并提交回复作者的新邮件来关闭用户通信循环。自动回复形式的一个示例是消息处置通知（MDN），它通知作者收件人对消息的处理。（见第4.1节。）
Also called "Bounce Handler", the Return Handler is a special form of Recipient tasked with servicing notifications generated by the MHS as it transfers or delivers the message. (See Figure 3.) These notices can be about failures or completions and are sent to an address that is specified by the Originator. This Return Handling address (also known as a Return Address) might have no visible characteristics in common with the address of the Author or Originator.
返回处理程序也称为“反弹处理程序”，是一种特殊形式的收件人，其任务是在MHS传输或传递消息时为其生成的通知提供服务。（见图3。）这些通知可以是关于失败或完成的，并发送到发起者指定的地址。此回执处理地址（也称为回执地址）可能与作者或发起者的地址没有共同的可见特征。
A Mediator receives, aggregates, reformulates, and redistributes messages among Authors and Recipients who are the principals in (potentially) protracted exchanges. This activity is easily confused with the underlying MHS transfer exchanges. However, each serves very different purposes and operates in very different ways.
调解人在作为（潜在）长期交换主体的作者和接收者之间接收、聚合、重新编制和重新分发消息。该活动很容易与基础MHS传输交换混淆。然而，每一种服务的目的和运作方式都非常不同。
When mail is delivered to the Mediator specified in the RFC5321.RcptTo command for the original message, the MHS handles it the same way as for any other Recipient. In particular, the MHS sees each posting and delivery activity between sources and sinks as independent; it does not see subsequent re-posting as a continuation of a process. Because the Mediator originates messages, it can receive replies. Hence, when submitting a reformulated message, the Mediator is an Author, albeit an Author actually serving as an agent of one or more other Authors. So a Mediator really is a full-fledged User. Mediators are considered extensively in Section 5.
当邮件传递到原始邮件的RFC5321.RcptTo命令中指定的中介时，MHS将以与任何其他收件人相同的方式处理邮件。特别是，MHS认为源和汇之间的每个过账和交付活动是独立的；它不认为后续重新过账是流程的延续。因为中介程序生成消息，所以它可以接收回复。因此，在提交重新编写的消息时，调解人是作者，尽管实际上是作为一个或多个其他作者的代理的作者。因此，调解人实际上是一个成熟的用户。第5节广泛考虑了调解人。
A Mediator attempts to preserve the original Author's information in the message it reformulates but is permitted to make meaningful changes to the message content or envelope. The MHS sees a new message, but Users receive a message that they interpret as being from, or at least initiated by, the Author of the original message. The role of a Mediator is not limited to merely connecting other participants; the Mediator is responsible for the new message.
调解人试图在重新编写的消息中保留原始作者的信息，但允许对消息内容或信封进行有意义的更改。MHS看到一条新消息，但用户收到一条消息，他们将其解释为来自原始消息的作者，或至少由原始消息的作者发起。调解人的作用不仅限于联系其他参与者；调解人负责新消息。
A Mediator's role is complex and contingent, for example, modifying and adding content or regulating which Users are allowed to participate and when. The common example of this role is a group Mailing List. In a more complex use, a sequence of Mediators could perform a sequence of formal steps, such as reviewing, modifying, and approving a purchase request.
调解人的角色是复杂的和偶然的，例如，修改和添加内容，或者规定允许哪些用户参与以及何时参与。此角色的常见示例是组邮件列表。在更复杂的使用中，一系列中介人可以执行一系列正式步骤，如审查、修改和批准采购请求。
A Gateway is a particularly interesting form of Mediator. It is a hybrid of User and Relay that connects heterogeneous mail services. Its purpose is to emulate a Relay. For a detailed discussion, see Section 2.2.3.
网关是一种特别有趣的中介形式。它是连接异构邮件服务的用户和中继的混合体。其目的是模拟继电器。有关详细讨论，请参见第2.2.3节。
The Message Handling Service (MHS) performs a single end-to-end transfer on behalf of the Author to reach the Recipient addresses specified in the original RFC5321.RcptTo commands. Exchanges that are either mediated or iterative and protracted, such as those used for collaboration over time, are handled by the User Actors, not by the MHS Actors. As a pragmatic heuristic MHS Actors generate, modify, or look at only transfer data, rather than the entire message.
消息处理服务（MHS）代表作者执行单个端到端传输，以到达原始RFC5321.RcptTo命令中指定的收件人地址。中介的、迭代的和长期的交换，例如用于长期协作的交换，由用户参与者处理，而不是由MHS参与者处理。作为一种实用的启发式方法，MHS参与者只生成、修改或查看传输数据，而不是整个消息。
Figure 3 shows the relationships among transfer participants in Internet Mail. Although it shows the Originator (labeled Origin) as distinct from the Author, and Receiver (labeled Recv) as distinct from Recipient, each pair of roles usually has the same Actor. Transfers typically entail one or more Relays. However, direct delivery from the Originator to Receiver is possible. Intra-organization mail services usually have only one Relay.
图3显示了Internet邮件中转账参与者之间的关系。虽然它显示了发起者（标记为Origin）与作者不同，接收者（标记为Recv）与接收者不同，但每对角色通常都有相同的参与者。传输通常需要一个或多个继电器。但是，发端人可以直接向接收方交付。组织内部邮件服务通常只有一个中继。
++==========++ ++===========++
|| Author || || Recipient ||
++====++====++ +--------+ ++===========++
|| | Return | /\
|| +-+------+ ||
\/ . ^ ||
+---------+ . . +---++---+
| | . . | |
/--+---------+----------------------------+--------+----\
| | | . . MHS | | |
| | Origin +<...... .................+ Recv | |
| | | ^ | | |
| +---++----+ . +--------+ |
| || . /\ |
| || ..............+.................. || |
| \/ . . . || |
| +-------+-+ +--+------+ +-+--++---+ |
| | Relay +=======>| Relay +=======>| Relay | |
| +---------+ +----++---+ +---------+ |
| || |
| || |
| \/ |
| +---------+ |
| | Gateway +-->... |
| +---------+ |
\-------------------------------------------------------/
++==========++ ++===========++
|| Author || || Recipient ||
++====++====++ +--------+ ++===========++
|| | Return | /\
|| +-+------+ ||
\/ . ^ ||
+---------+ . . +---++---+
| | . . | |
/--+---------+----------------------------+--------+----\
| | | . . MHS | | |
| | Origin +<...... .................+ Recv | |
| | | ^ | | |
| +---++----+ . +--------+ |
| || . /\ |
| || ..............+.................. || |
| \/ . . . || |
| +-------+-+ +--+------+ +-+--++---+ |
| | Relay +=======>| Relay +=======>| Relay | |
| +---------+ +----++---+ +---------+ |
| || |
| || |
| \/ |
| +---------+ |
| | Gateway +-->... |
| +---------+ |
\-------------------------------------------------------/
Legend: === and || lines indicate primary (possibly indirect) transfers or roles ... lines indicate supporting transfers or roles
图例：==和| |行表示主要（可能是间接）转移或角色。。。行表示支持转移或角色
Figure 3: Relationships among MHS Actors
图3:MHS参与者之间的关系
The Originator ensures that a message is valid for posting and then submits it to a Relay. A message is valid if it conforms to both Internet Mail standards and local operational policies. The Originator can simply review the message for conformance and reject it if it finds errors, or it can create some or all of the necessary information. In effect, the Originator is responsible for the functions of the Mail Submission Agent.
发起者确保消息对发布有效，然后将其提交给中继。如果消息同时符合Internet邮件标准和本地操作策略，则该消息有效。发端人可以简单地检查消息的一致性，如果发现错误则拒绝消息，或者可以创建一些或所有必要的信息。实际上，发起人负责邮件提交代理的功能。
The Originator operates with dual allegiance. It serves the Author and can be the same entity. But its role in assuring validity means that it also represents the local operator of the MHS, that is, the local ADministrative Management Domain (ADMD).
发起者具有双重忠诚。它为作者服务，可以是同一个实体。但它在确保有效性方面的作用意味着它还代表MHS的本地运营商，即本地行政管理域（ADMD）。
The Originator also performs any post-submission, Author-related administrative tasks associated with message transfer and delivery. Notably, these tasks pertain to sending error and delivery notices, enforcing local policies, and dealing with messages from the Author that prove to be problematic for the Internet. The Originator is accountable for the message content, even when it is not responsible for it. The Author creates the message, but the Originator handles any transmission issues with it.
发起人还执行与邮件传输和传递相关的任何提交后、作者相关的管理任务。值得注意的是，这些任务涉及发送错误和交付通知、强制执行本地策略以及处理来自作者的消息，这些消息被证明对互联网有问题。发起者对消息内容负责，即使它不负责。作者创建消息，但发起者处理消息的任何传输问题。
The Relay performs MHS-level transfer-service routing and store-and-forward by transmitting or retransmitting the message to its Recipients. The Relay adds trace information [RFC2505] but does not modify the envelope information or the message content semantics. It can modify message content representation, such as changing the form of transfer encoding from binary to text, but only as required to meet the capabilities of the next hop in the MHS.
中继器执行MHS级别的传输服务路由，并通过将消息传输或重传给其接收者来存储和转发。中继添加跟踪信息[RFC2505]，但不修改信封信息或消息内容语义。它可以修改消息内容表示，例如将传输编码的形式从二进制更改为文本，但只能根据需要满足MHS中下一跳的功能。
A Message Handling System (MHS) network consists of a set of Relays. This network is above any underlying packet-switching network that might be used and below any Gateways or other Mediators.
消息处理系统（MHS）网络由一组继电器组成。该网络位于可能使用的任何底层分组交换网络之上，位于任何网关或其他中介器之下。
In other words, email scenarios can involve three distinct architectural layers, each providing its own type of data of store-and-forward service:
换句话说，电子邮件场景可能涉及三个不同的体系结构层，每个层提供自己类型的存储转发服务数据：
* User Mediators
* 用户中介
* MHS Relays
* MHS继电器
* Packet Switches
* 分组交换机
The bottom layer is the Internet's IP service. The most basic email scenarios involve Relays and Switches.
底层是互联网的IP服务。最基本的电子邮件场景包括中继和开关。
When a Relay stops attempting to transfer a message, it becomes an Author because it sends an error message to the Return Address. The potential for looping is avoided by omitting a Return Address from this message.
当中继停止尝试传输消息时，它将成为作者，因为它向返回地址发送错误消息。通过在此消息中省略返回地址，可以避免循环的可能性。
A Gateway is a hybrid of User and Relay that connects heterogeneous mail services. Its purpose is to emulate a Relay and the closer it comes to this, the better. A Gateway operates as a User when it needs the ability to modify message content.
网关是连接异构邮件服务的用户和中继的混合体。它的目的是模拟一个继电器，越接近它，效果越好。当网关需要修改消息内容时，它作为用户运行。
Differences between mail services can be as small as minor syntax variations, but they usually encompass significant, semantic distinctions. One difference could be email addresses that are hierarchical and machine-specific rather than a flat, global namespace. Another difference could be support for text-only content or multimedia. Hence the Relay function in a Gateway presents a significant design challenge if the resulting performance is to be seen as nearly seamless. The challenge is to ensure User-to-User functionality between the services, despite differences in their syntax and semantics.
邮件服务之间的差异可以是微小的语法变化，但它们通常包含显著的语义差异。一个区别可能是电子邮件地址是分层的和特定于机器的，而不是一个平面的全局名称空间。另一个区别可能是支持纯文本内容或多媒体。因此，如果要将产生的性能视为几乎无缝的，那么网关中的中继功能将带来重大的设计挑战。挑战在于确保服务之间的用户对用户功能，尽管它们在语法和语义上存在差异。
The basic test of Gateway design is whether an Author on one side of a Gateway can send a useful message to a Recipient on the other side, without requiring changes to any components in the Author's or Recipient's mail services other than adding the Gateway. To each of these otherwise independent services, the Gateway appears to be a native participant. But the ultimate test of Gateway design is whether the Author and Recipient can sustain a dialogue. In particular, can a Recipient's MUA automatically formulate a valid Reply that will reach the Author?
网关设计的基本测试是，网关一侧的作者是否可以向另一侧的收件人发送有用的消息，而无需更改作者或收件人邮件服务中的任何组件（添加网关除外）。对于这些独立服务中的每一个，网关似乎都是本地参与者。但网关设计的最终测试是作者和接收者是否能够保持对话。特别是，收件人的MUA能否自动制定有效的回复，并将其送达作者？
The Receiver performs final delivery or sends the message to an alternate address. It can also perform filtering and other policy enforcement immediately before or after delivery.
接收方执行最终传递或将消息发送到备用地址。它还可以在交付之前或之后立即执行筛选和其他策略实施。
Administrative Actors can be associated with different organizations, each with its own administrative authority. This operational independence, coupled with the need for interaction between groups, provides the motivation to distinguish among ADministrative Management Domains (ADMDs). Each ADMD can have vastly different operating policies and trust-based decision-making. One obvious example is the distinction between mail that is exchanged within an organization and mail that is exchanged between independent organizations. The rules for handling both types of traffic tend to be quite different. That difference requires defining the boundaries of each, and this requires the ADMD construct.
行政参与者可以与不同的组织相关联，每个组织都有自己的行政权限。这种运作上的独立性，加上组之间的交互需要，为区分不同的管理域（ADMD）提供了动力。每个ADMD都可以有截然不同的运营策略和基于信任的决策。一个明显的例子是组织内部交换的邮件与独立组织之间交换的邮件之间的区别。处理这两类交通的规则往往大不相同。这种差异需要定义每个对象的边界，这需要ADMD构造。
Operation of Internet Mail services is carried out by different providers (or operators). Each can be an independent ADMD. This independence of administrative decision-making defines boundaries that distinguish different portions of the Internet Mail service. A department that operates a local Relay, an IT department that operates an enterprise Relay, and an ISP that operates a public shared email service can be configured into many combinations of
互联网邮件服务的运营由不同的提供商（或运营商）进行。每个都可以是独立的ADMD。这种行政决策的独立性定义了区分Internet邮件服务不同部分的边界。运营本地中继的部门、运营企业中继的IT部门以及运营公共共享电子邮件服务的ISP可以配置为以下多种组合：
administrative and operational relationships. Each is a distinct ADMD, potentially having a complex arrangement of functional components. Figure 4 depicts relationships among ADMDs. The benefit of the ADMD construct is that it facilitates discussion about designs, policies, and operations that need to distinguish between internal issues and external ones.
行政和业务关系。每个都是一个不同的ADMD，可能具有复杂的功能组件排列。图4描述了ADMD之间的关系。ADMD结构的好处在于，它有助于讨论需要区分内部问题和外部问题的设计、策略和操作。
The architectural impact of the need for boundaries between ADMDs is discussed in [Tussle]. Most significant is that the entities communicating across ADMD boundaries typically have the added burden of enforcing organizational policies concerning external communications. At a more mundane level, routing mail between ADMDs can be an issue, such as needing to route mail between organizational partners over specially trusted paths.
在[Tussle]中讨论了ADMD之间需要边界的架构影响。最重要的是，跨ADMD边界进行通信的实体通常会增加强制执行有关外部通信的组织策略的负担。在更普通的层面上，在ADMD之间路由邮件可能是一个问题，例如需要通过特别受信任的路径在组织合作伙伴之间路由邮件。
These are three basic types of ADMDs:
以下是ADMD的三种基本类型：
Edge: Independent transfer services in networks at the edge of the open Internet Mail service.
边缘：在开放的互联网邮件服务的边缘网络中的独立传输服务。
Consumer: Might be a type of Edge service, as is common for web-based email access.
消费者：可能是一种边缘服务，这在基于web的电子邮件访问中很常见。
Transit: Mail Service Providers (MSPs) that offer value-added capabilities for Edge ADMDs, such as aggregation and filtering.
传输：为边缘ADMD提供增值功能（如聚合和筛选）的邮件服务提供商（MSP）。
The mail-level transit service is different from packet-level switching. End-to-end packet transfers usually go through intermediate routers; email exchange across the open Internet can be directly between the Boundary MTAs of Edge ADMDs. This distinction between direct and indirect interaction highlights the differences discussed in Section 2.2.2.
邮件级传输服务不同于包级交换。端到端数据包传输通常通过中间路由器进行；开放式Internet上的电子邮件交换可以直接在Edge ADMD的边界MTA之间进行。直接和间接相互作用之间的区别突出了第2.2.2节中讨论的差异。
+--------+ +---------+ +-------+ +-----------+
| ADMD1 |<===>| ADMD2 |<===>| ADMD3 |<===>| ADMD4 |
| ----- | | ----- | | ----- | | ----- |
| | | | | | | |
| Author | | | | | | Recipient |
| . | | | | | | ^ |
| V | | | | | | . |
| Edge..+....>|.Transit.+....>|-Edge..+....>|..Consumer |
| | | | | | | |
+--------+ +---------+ +-------+ +-----------+
+--------+ +---------+ +-------+ +-----------+
| ADMD1 |<===>| ADMD2 |<===>| ADMD3 |<===>| ADMD4 |
| ----- | | ----- | | ----- | | ----- |
| | | | | | | |
| Author | | | | | | Recipient |
| . | | | | | | ^ |
| V | | | | | | . |
| Edge..+....>|.Transit.+....>|-Edge..+....>|..Consumer |
| | | | | | | |
+--------+ +---------+ +-------+ +-----------+
Legend: === lines indicate primary (possibly indirect) transfers or roles ... lines indicate supporting transfers or roles
图例：==行表示主要（可能是间接）传输或角色。。。行表示支持转移或角色
Figure 4: Administrative Domain (ADMD) Example
图4：管理域（ADMD）示例
Edge networks can use proprietary email standards internally. However, the distinction between Transit network and Edge network transfer services is significant because it highlights the need for concern over interaction and protection between independent administrations. In particular, this distinction calls for additional care in assessing the transitions of responsibility and the accountability and authorization relationships among participants in message transfer.
Edge networks可以在内部使用专有的电子邮件标准。然而，公交网络和边缘网络传输服务之间的区别非常重要，因为这突出了对独立管理机构之间的互动和保护的关注。特别是，这种区别要求在评估责任转移以及信息传输参与者之间的责任和授权关系时更加谨慎。
The interactions of ADMD components are subject to the policies of that domain, which cover concerns such as these:
ADMD组件的交互受该领域政策的约束，这些政策涵盖以下问题：
* Reliability
* 可靠性
* Access control
* 访问控制
* Accountability
* 责任
* Content evaluation and modification
* 内容评估和修改
These policies can be implemented in different functional components, according to the needs of the ADMD. For example, see [RFC5068].
根据ADMD的需要，这些策略可以在不同的功能组件中实现。例如，请参见[RFC5068]。
Consumer, Edge, and Transit services can be offered by providers that operate component services or sets of services. Further, it is possible for one ADMD to host services for other ADMDs.
消费者、边缘和运输服务可以由运营组件服务或服务集的提供商提供。此外，一个ADMD可以为其他ADMD托管服务。
These are common examples of ADMDs:
以下是ADMD的常见示例：
Enterprise Service Providers:
企业服务提供商：
These ADMDs operate the internal data and/or the mail services within an organization.
这些ADMD操作组织内的内部数据和/或邮件服务。
Internet Service Providers (ISP):
互联网服务提供商（ISP）：
These ADMDs operate the underlying data communication services, which are used by one or more Relay and User. ISPs are not responsible for performing email functions, but they can provide an environment in which those functions can be performed.
这些ADMD操作一个或多个中继和用户使用的底层数据通信服务。ISP不负责执行电子邮件功能，但他们可以提供执行这些功能的环境。
Mail Service Providers:
邮件服务供应商：
These ADMDs operate email services, such as for consumers or client companies.
这些ADMD提供电子邮件服务，例如为消费者或客户公司提供电子邮件服务。
Practical operational concerns demand that providers be involved in administration and enforcement issues. This involvement can extend to operators of lower-level packet services.
实际操作问题要求供应商参与管理和执行问题。这种参与可以扩展到较低级别分组服务的运营商。
The forms of identity used by Internet Mail are: mailbox, domain name, message-ID, and ENVID (envelope identifier). Each is globally unique.
Internet邮件使用的身份形式有：邮箱、域名、邮件ID和ENVID（信封标识符）。每个都是全球唯一的。
"A mailbox receives mail. It is a conceptual entity that does not necessarily pertain to file storage." [RFC5322]
“邮箱接收邮件。它是一个概念实体，不一定属于文件存储。”[RFC5322]
A mailbox is specified as an Internet Mail address <addr-spec>. It has two distinct parts, separated by an at-sign (@). The right side is a globally interpreted domain name associated with an ADMD. Domain names are discussed in Section 3.3. Formal Internet Mail addressing syntax can support source routes to indicate the path through which a message ought to be sent. The use of source routes is not common and has been deprecated in [RFC5321].
邮箱被指定为Internet邮件地址<addr spec>。它有两个不同的部分，由at符号（@）分隔。右侧是与ADMD关联的全局解释域名。第3.3节讨论了域名。正式的Internet邮件寻址语法可以支持源路由，以指示消息应该通过的路径。源路由的使用并不常见，在[RFC5321]中已被弃用。
The portion to the left of the at-sign contains a string that is globally opaque and is called the <local-part>. It is interpreted only by the entity specified by the address's domain name. Except as noted later in this section, all other entities treat the <local-part> as an uninterpreted literal string and preserve all
at符号左侧的部分包含一个全局不透明的字符串，称为<local part>。它仅由地址的域名指定的实体进行解释。除本节后面所述之外，所有其他实体都将<local part>视为未解释的文本字符串，并保留所有
of its original details. As such, its public distribution is equivalent to sending a Web browser "cookie" that is only interpreted upon being returned to its creator.
它的原始细节。因此，它的公开发布相当于发送一个Web浏览器“cookie”，该“cookie”只有在返回到其创建者时才会被解释。
Some local-part values have been standardized for contacting personnel at an organization. These names cover common operations and business functions [RFC2142].
一些局部零件值已标准化，以便与组织中的人员联系。这些名称包括常见的操作和业务功能[RFC2142]。
It is common for sites to have local structuring conventions for the left-hand side, <local-part>, of an <addr-spec>. This permits sub-addressing, such as for distinguishing different discussion groups used by the same participant. However, it is worth stressing that these conventions are strictly private to the User's organization and are not interpreted by any domain except the one listed in the right side of the <addr-spec>. The exceptions are those specialized services that conform to public, standardized conventions, as noted below.
站点通常在<addr spec>的左侧<local part>具有本地结构约定。这允许子寻址，例如用于区分同一参与者使用的不同讨论组。但是，值得强调的是，这些约定对用户的组织来说是严格保密的，除<addr spec>右侧列出的域外，任何域都不会解释这些约定。例外情况是符合公共标准化惯例的专业服务，如下所述。
Basic email addressing defines the <local-part> as being globally opaque. However, there are some uses of email that add a standardized, global schema to the value, such as between an Author and a Gateway. The <local-part> details remain invisible to the public email transfer infrastructure, but provide addressing and handling instructions for further processing by the Gateway. Standardized examples of these conventions are the telephone numbering formats for the Voice Profile for Internet Mail (VPIM) [RFC3801], such as:
基本电子邮件地址将<local part>定义为全局不透明。然而，电子邮件的一些用途是向值添加标准化的全局模式，例如在作者和网关之间。<local part>详细信息对公共电子邮件传输基础设施不可见，但为网关的进一步处理提供寻址和处理说明。这些约定的标准化示例是互联网邮件语音配置文件（VPIM）[RFC3801]的电话号码格式，例如：
+16137637582@vpim.example.com,
+16137637582@vpim.example.com,
and iFax ([RFC3192], [RFC4143] such as:
和iFax（[RFC3192]，[RFC4143]如：
FAX=+12027653000/T33S=1387@ifax.example.com.
传真=+12027653000/T33S=1387@ifax.example.com.
Email addresses are being used far beyond their original role in email transfer and delivery. In practical terms, an email address string has become the common identifier for representing online identity. Hence, it is essential to be clear about both the nature and role of an identity string in a particular context and the entity responsible for setting that string. For example, see Sections 4.1.4, 4.3.3, and 5.
电子邮件地址的使用远远超出了其在电子邮件传输和传递中的原始角色。实际上，电子邮件地址字符串已经成为表示在线身份的通用标识符。因此，必须清楚标识字符串在特定上下文中的性质和作用，以及负责设置该字符串的实体。例如，参见第4.1.4节、第4.3.3节和第5节。
A domain name is a global reference to an Internet resource, such as a host, a service, or a network. A domain name usually maps to one or more IP Addresses. Conceptually, the name can encompass an organization, a collection of machines integrated into a homogeneous service, or a single machine. A domain name can be administered to refer to an individual User, but this is not common practice. The name is structured as a hierarchical sequence of labels, separated by dots (.), with the top of the hierarchy being on the right end of the sequence. There can be many names in the sequence -- that is, the depth of the hierarchy can be substantial. Domain names are defined and operated through the Domain Name System (DNS) ([RFC1034], [RFC1035], [RFC2181]).
域名是对Internet资源（如主机、服务或网络）的全局引用。域名通常映射到一个或多个IP地址。从概念上讲，名称可以包含一个组织、集成到同构服务中的一组机器或一台机器。可以管理域名以引用单个用户，但这不是常见做法。名称的结构为标签的层次序列，由点（.）分隔，层次的顶部位于序列的右端。序列中可能有许多名称——也就是说，层次结构的深度可能很大。域名通过域名系统（DNS）（[RFC1034]、[RFC1035]、[RFC2181]）进行定义和操作。
When not part of a mailbox address, a domain name is used in Internet Mail to refer to the ADMD or to the host that took action upon the message, such as providing the administrative scope for a message identifier or performing transfer processing.
如果域名不是邮箱地址的一部分，则在Internet邮件中使用域名来引用ADMD或对邮件采取操作的主机，例如为邮件标识符提供管理范围或执行传输处理。
There are two standardized tags for identifying messages: Message-ID: and ENVID. A Message-ID: pertains to content, and an ENVID pertains to transfer.
有两个用于标识消息的标准化标记：Message ID:和ENVID。消息ID：属于内容，ENVID属于传输。
IMF provides for, at most, a single Message-ID:. The Message-ID: for a single message, which is a user-level IMF tag, has a variety of uses including threading, aiding identification of duplicates, and DSN (Delivery Status Notification) tracking. The Originator assigns the Message-ID:. The Recipient's ADMD is the intended consumer of the Message-ID:, although any Actor along the transfer path can use it.
IMF最多提供一个消息ID:。消息ID：对于单个消息，它是一个用户级别的IMF标记，具有多种用途，包括线程、辅助识别重复项和DSN（传递状态通知）跟踪。发起人分配消息ID:。收件人的ADMD是消息ID:的预期使用者，尽管传输路径上的任何参与者都可以使用它。
Message-ID: is globally unique. Its format is similar to that of a mailbox, with two distinct parts separated by an at-sign (@). Typically, the right side specifies the ADMD or host that assigns the identifier, and the left side contains a string that is globally opaque and serves to uniquely identify the message within the domain referenced on the right side. The duration of uniqueness for the message identifier is undefined.
消息ID:是全局唯一的。它的格式类似于邮箱，有两个不同的部分由at符号（@）分隔。通常，右侧指定分配标识符的ADMD或主机，左侧包含一个全局不透明的字符串，用于在右侧引用的域中唯一标识消息。消息标识符的唯一性持续时间未定义。
When a message is revised in any way, the decision whether to assign a new Message-ID: requires a subjective assessment to determine whether the editorial content has been changed enough to constitute a new message. [RFC5322] states that "a message identifier pertains to
当以任何方式修改消息时，是否分配新消息ID:的决定需要进行主观评估，以确定编辑内容是否已更改到足以构成新消息。[RFC5322]声明“消息标识符与
exactly one version of a particular message; subsequent revisions to the message each receive new message identifiers." Yet experience suggests that some flexibility is needed. An impossible test is whether the Recipient will consider the new message to be equivalent to the old one. For most components of Internet Mail, there is no way to predict a specific Recipient's preferences on this matter. Both creating and failing to create a new Message-ID: have their downsides.
特定信息的一个版本；消息的后续修订都会接收新的消息标识符。“然而，经验表明，需要一些灵活性。一个不可能的测试是接收方是否会认为新消息与旧消息相当。对于Internet邮件的大多数组成部分，无法预测特定收件人在这方面的偏好。创建和未能创建新的消息ID都有其缺点。
Here are some guidelines and examples:
以下是一些指南和示例：
o If a message is changed only in form, such as character encoding, it is still the same message.
o 如果消息仅在形式（如字符编码）上更改，则它仍然是相同的消息。
o If a message has minor additions to the content, such as a Mailing List tag at the beginning of the RFC5322.Subject header field, or some Mailing List administrative information added to the end of the primary body part text, it is probably the same message.
o 如果消息的内容中添加了一些次要内容，例如RFC5322.Subject标题字段开头的邮件列表标记，或者在正文部分文本末尾添加了一些邮件列表管理信息，则可能是同一消息。
o If a message has viruses deleted from it, it is probably the same message.
o 如果邮件中删除了病毒，则可能是同一封邮件。
o If a message has offensive words deleted from it, some Recipients will consider it the same message, but some will not.
o 如果消息中删除了冒犯的话，一些收件人会认为它是同一条消息，但有些则不会。
o If a message is translated into a different language, some Recipients will consider it the same message, but some will not.
o 如果消息被翻译成不同的语言，一些收件人会认为它是相同的消息，但有些不会。
o If a message is included in a digest of messages, the digest constitutes a new message.
o 如果消息摘要中包含消息，则该摘要将构成新消息。
o If a message is forwarded by a Recipient, what is forwarded is a new message.
o 如果邮件由收件人转发，则转发的是新邮件。
o If a message is "redirected", such as using IMF "Resent-*" header fields, some Recipients will consider it the same message, but some will not.
o 如果消息是“重定向”的，例如使用IMF“Reunt**”标头字段，一些收件人会认为它是同一条消息，但有些则不会。
The absence of both objective, precise criteria for regenerating a Message-ID: and strong protection associated with the string means that the presence of an ID can permit an assessment that is marginally better than a heuristic, but the ID certainly has no value on its own for strict formal reference or comparison. For that reason, the Message-ID: is not intended to be used for any function that has security implications.
没有客观、准确的标准来重新生成消息ID：以及与字符串相关的强大保护意味着ID的存在可以允许进行比启发式略好的评估，但ID本身对于严格的形式参考或比较肯定没有价值。因此，消息ID:不用于任何具有安全含义的函数。
The ENVID (envelope identifier) can be used for message-tracking purposes ([RFC3885], [RFC3464]) concerning a single posting/delivery transfer. The ENVID labels a single transit of the MHS by a specific message. So, the ENVID is used for one message posting until that message is delivered. A re-posting of the message, such as by a Mediator, does not reuse that ENVID, but can use a new one, even though the message might legitimately retain its original Message-ID:.
ENVID（信封标识符）可用于单次投递/传递的邮件跟踪目的（[RFC3885]、[RFC3464]）。ENVID通过特定消息标记MHS的单个传输。因此，ENVID用于发布一条消息，直到该消息被传递为止。消息的重新发布（如通过中介）不会重用该ENVID，但可以使用新的ENVID，即使消息可能合法地保留其原始消息ID:。
The format of an ENVID is free form. Although its creator might choose to impose structure on the string, none is imposed by Internet standards. By implication, the scope of the string is defined by the domain name of the Return Address.
ENVID的格式是自由格式的。尽管它的创建者可能会选择将结构强加给字符串，但没有一个是由互联网标准强加的。通过暗示，字符串的范围由返回地址的域名定义。
The Internet Mail architecture comprises six basic types of functionality, which are arranged to support a store-and-forward service. As shown in Figure 5, each type can have multiple instances, some of which represent specialized roles. This section considers the activities and relationships among these components, and the Internet Mail standards that apply to them.
Internet邮件体系结构包括六种基本类型的功能，它们被安排为支持存储转发服务。如图5所示，每种类型都可以有多个实例，其中一些实例表示专门的角色。本节讨论这些组件之间的活动和关系，以及适用于它们的Internet邮件标准。
Message
消息
Message User Agent (MUA)
消息用户代理（MUA）
Author MUA (aMUA)
作者穆阿（阿穆阿）
Recipient MUA (rMUA)
收件人MUA（rMUA）
Message Submission Agent (MSA)
邮件提交代理（MSA）
Author-focused MSA functions (aMSA)
以作者为中心的MSA功能（aMSA）
MHS-focused MSA functions (hMSA)
MHS聚焦MSA功能（hMSA）
Message Transfer Agent (MTA)
邮件传输代理（MTA）
Message Delivery Agent (MDA)
消息传递代理（MDA）
Recipient-focused MDA functions (rMDA)
以收件人为中心的MDA功能（rMDA）
MHS-focused MDA functions (hMDA)
以MHS为重点的MDA功能（hMDA）
Message Store (MS)
消息存储（MS）
Author MS (aMS)
作者MS（aMS）
Recipient MS (rMS)
收件人MS（rMS）
This figure shows function modules and the standardized protocols used between them.
此图显示了功能模块及其之间使用的标准化协议。
++========++
|| || +-------+
...........++ aMUA ||<............................+ Disp |
. || || +-------+
. ++=+==+===++ ^
. local,imap}| |{smtp,submission .
. +-----+ | | +--------+ .
. | aMS |<---+ | ........................>| Return | .
. +-----+ | . +--------+ .
. | . ***************** ^ .
. +-----V-.----*------------+ * . .
. MSA | +-------+ * +------+ | * . .
. | | aMSA +-(S)->| hMSA | | * . .
. | +-------+ * +--+---+ | * . .
V +------------*------+-----+ * . .
//==========\\ * V {smtp * . .
|| MESSAGE || * +------+ * //===+===\\ .
||----------|| MHS * | MTA | * || dsn || .
|| ENVELOPE || * +--+---+ * \\=======// .
|| smtp || * V {smtp * ^ ^ .
|| CONTENT || * +------+ * . . //==+==\\
|| imf || * | MTA +....*...... . || mdn ||
|| mime || * +--+---+ * . \\=====//
\\==========// * smtp}| {local * . ^
. MDA * | {lmtp * . .
. +----------------+------V-----+ * . .
. | +----------+ * +------+ | * . .
. | | | * | | +..*.......... .
. | | rMDA |<-(D)--+ hMDA | | * .
. | | | * | | |<.*........ .
. | +-+------+-+ * +------+ | * . .
. +------+---------*------------+ * . .
. smtp,local}| ***************** . .
. V . .
. +-----+ //===+===\\ .
. | rMS | || sieve || .
. +--+--+ \\=======// .
. |{imap,pop,local ^ .
. V . .
. ++==========++ . .
. || || . .
.......>|| rMUA ++........................... .
|| ++...................................
++==========++
++========++
|| || +-------+
...........++ aMUA ||<............................+ Disp |
. || || +-------+
. ++=+==+===++ ^
. local,imap}| |{smtp,submission .
. +-----+ | | +--------+ .
. | aMS |<---+ | ........................>| Return | .
. +-----+ | . +--------+ .
. | . ***************** ^ .
. +-----V-.----*------------+ * . .
. MSA | +-------+ * +------+ | * . .
. | | aMSA +-(S)->| hMSA | | * . .
. | +-------+ * +--+---+ | * . .
V +------------*------+-----+ * . .
//==========\\ * V {smtp * . .
|| MESSAGE || * +------+ * //===+===\\ .
||----------|| MHS * | MTA | * || dsn || .
|| ENVELOPE || * +--+---+ * \\=======// .
|| smtp || * V {smtp * ^ ^ .
|| CONTENT || * +------+ * . . //==+==\\
|| imf || * | MTA +....*...... . || mdn ||
|| mime || * +--+---+ * . \\=====//
\\==========// * smtp}| {local * . ^
. MDA * | {lmtp * . .
. +----------------+------V-----+ * . .
. | +----------+ * +------+ | * . .
. | | | * | | +..*.......... .
. | | rMDA |<-(D)--+ hMDA | | * .
. | | | * | | |<.*........ .
. | +-+------+-+ * +------+ | * . .
. +------+---------*------------+ * . .
. smtp,local}| ***************** . .
. V . .
. +-----+ //===+===\\ .
. | rMS | || sieve || .
. +--+--+ \\=======// .
. |{imap,pop,local ^ .
. V . .
. ++==========++ . .
. || || . .
.......>|| rMUA ++........................... .
|| ++...................................
++==========++
Legend: --- lines indicate primary (possibly indirect)
transfers or roles
=== boxes indicate data objects
Legend: --- lines indicate primary (possibly indirect)
transfers or roles
=== boxes indicate data objects
... lines indicate supporting transfers or roles
*** lines indicate aggregated service
... lines indicate supporting transfers or roles
*** lines indicate aggregated service
Figure 5: Protocols and Services
图5：协议和服务
The purpose of the Message Handling System (MHS) is to exchange an IMF message object among participants [RFC5322]. All of its underlying mechanisms serve to deliver that message from its Author to its Recipients. A message can be explicitly labeled as to its nature [RFC3458].
消息处理系统（MHS）的目的是在参与者之间交换IMF消息对象[RFC5322]。它的所有底层机制都用于将消息从作者传递给接收者。可以根据消息的性质明确标记消息[RFC3458]。
A message comprises a transit-handling envelope and the message content. The envelope contains information used by the MHS. The content is divided into a structured header and the body. The header comprises transit-handling trace information and structured fields that are part of the Author's message content. The body can be unstructured lines of text or a tree of multimedia subordinate objects, called "body-parts" or, popularly, "attachments". [RFC2045], [RFC2046], [RFC2047], [RFC4288], [RFC4289], [RFC2049].
消息包括传输处理信封和消息内容。信封包含MHS使用的信息。内容分为结构化标题和正文。标头包含传输处理跟踪信息和结构化字段，这些字段是作者消息内容的一部分。正文可以是非结构化的文本行或多媒体从属对象树，称为“正文部分”，或者通常称为“附件”。[RFC2045]、[RFC2046]、[RFC2047]、[RFC4288]、[RFC4289]、[RFC2049]。
In addition, Internet Mail has a few conventions for special control data, notably:
此外，Internet Mail对特殊控制数据有一些约定，特别是：
Delivery Status Notification (DSN):
交付状态通知（DSN）：
A Delivery Status Notification (DSN) is a message that can be generated by the MHS (MSA, MTA, or MDA) and sent to the RFC5321.MailFrom address. MDA and MTA are shown as sources of DSNs in Figure 5, and the destination is shown as Returns. DSNs provide information about message transit, such as transfer errors or successful delivery [RFC3461].
传递状态通知（DSN）是可由MHS（MSA、MTA或MDA）生成并发送到RFC5321.MailFrom地址的消息。MDA和MTA在图5中显示为DSN的源，目标显示为返回。DSN提供有关消息传输的信息，例如传输错误或成功传递[RFC3461]。
Message Disposition Notification (MDN):
消息处置通知（MDN）：
A Message Disposition Notification (MDN) is a message that provides information about post-delivery processing, such as indicating that the message has been displayed [RFC3798] or the form of content that can be supported [RFC3297]. It can be generated by an rMUA and is sent to the Disposition-Notification-To addresses. The mailbox for this is shown as Disp in Figure 5.
消息处置通知（MDN）是一种提供有关传递后处理信息的消息，例如指示消息已显示[RFC3798]或可支持的内容形式[RFC3297]。它可以由rMUA生成，并发送到处置通知地址。用于此的邮箱如图5中的Disp所示。
Message Filtering (SIEVE):
消息过滤（筛选）：
Sieve is a scripting language used to specify conditions for differential handling of mail, typically at the time of delivery [RFC5228]. Scripts can be conveyed in a variety of ways, such as a MIME part in a message. Figure 5 shows a Sieve script going from the rMUA to the MDA. However, filtering can be done at many different points along the transit path, and any one or more of them might be subject to Sieve directives, especially within a single ADMD. Figure 5 shows only one relationship, for (relative) simplicity.
Sieve是一种脚本语言，用于指定邮件差异处理的条件，通常在邮件交付时使用[RFC5228]。脚本可以以多种方式传递，例如消息中的MIME部分。图5显示了从rMUA到MDA的筛选脚本。但是，可以在传输路径上的多个不同点进行过滤，其中任何一个或多个点都可能受到筛选指令的约束，尤其是在单个ADMD中。图5仅显示了一种关系，以实现（相对）简单性。
Internet Mail has a fragmented framework for transit-related handling information. Information that is used directly by the MHS is called the "envelope". It directs handling activities by the transfer service and is carried in transfer-service commands. That is, the envelope exists in the transfer protocol SMTP [RFC5321].
互联网邮件有一个碎片化的框架，用于处理与运输相关的信息。MHS直接使用的信息称为“信封”。它指导转运服务的搬运活动，并在转运服务命令中进行。也就是说，信封存在于传输协议SMTP[RFC5321]中。
Trace information, such as RFC5322.Received, is recorded in the message header and is not subsequently altered [RFC5322].
跟踪信息（如RFC5322.Received）记录在消息头中，随后不会更改[RFC5322]。
Header fields are attribute name/value pairs that cover an extensible range of email-service parameters, structured user content, and user transaction meta-information. The core set of header fields is defined in [RFC5322]. It is common practice to extend this set for different applications. Procedures for registering header fields are defined in [RFC3864]. An extensive set of existing header field registrations is provided in [RFC4021].
标题字段是属性名称/值对，涵盖电子邮件服务参数、结构化用户内容和用户事务元信息的可扩展范围。标题字段的核心集在[RFC5322]中定义。通常的做法是为不同的应用扩展此集合。[RFC3864]中定义了注册标题字段的步骤。[RFC4021]中提供了一组广泛的现有标题字段注册。
One danger of placing additional information in header fields is that Gateways often alter or delete them.
在头字段中放置附加信息的一个危险是网关经常更改或删除它们。
The body of a message might be lines of ASCII text or a hierarchically structured composition of multimedia body part attachments using MIME ([RFC2045], [RFC2046], [RFC2047], [RFC4288], and [RFC2049]).
消息正文可以是ASCII文本行，也可以是使用MIME的多媒体正文部分附件的层次结构组合（[RFC2045]、[RFC2046]、[RFC2047]、[RFC4288]和[RFC2049]）。
Table 1 lists the core identifiers present in a message during transit.
表1列出了在传输过程中出现在消息中的核心标识符。
+----------------------+----------------+---------------------------+
| Layer | Field | Set By |
+----------------------+----------------+---------------------------+
| Message Body | MIME Header | Author |
| Message header | From: | Author |
| fields | | |
| | Sender: | Originator |
| | Reply-To: | Author |
| | To:, CC:, BCC: | Author |
| | Message-ID: | Originator |
| | Received: | Originator, Relay, |
| | | Receiver |
| | Return-Path: | MDA, from MailFrom |
| | Resent-*: | Mediator |
| | List-Id: | Mediator |
| | List-*: | Mediator |
| SMTP | HELO/EHLO | Latest Relay Client |
| | ENVID | Originator |
| | MailFrom | Originator |
| | RcptTo | Author |
| | ORCPT | Originator |
| IP | Source Address | Latest Relay Client |
+----------------------+----------------+---------------------------+
+----------------------+----------------+---------------------------+
| Layer | Field | Set By |
+----------------------+----------------+---------------------------+
| Message Body | MIME Header | Author |
| Message header | From: | Author |
| fields | | |
| | Sender: | Originator |
| | Reply-To: | Author |
| | To:, CC:, BCC: | Author |
| | Message-ID: | Originator |
| | Received: | Originator, Relay, |
| | | Receiver |
| | Return-Path: | MDA, from MailFrom |
| | Resent-*: | Mediator |
| | List-Id: | Mediator |
| | List-*: | Mediator |
| SMTP | HELO/EHLO | Latest Relay Client |
| | ENVID | Originator |
| | MailFrom | Originator |
| | RcptTo | Author |
| | ORCPT | Originator |
| IP | Source Address | Latest Relay Client |
+----------------------+----------------+---------------------------+
Legend: Layer - The part of the email architecture that uses the identifier.
图例：层-电子邮件体系结构中使用标识符的部分。
Field - The protocol construct that contains the identifier.
字段-包含标识符的协议构造。
Set By - The Actor role responsible for specifying the identifier value (and this can be different from the Actor that performs the fill-in function for the protocol construct).
Set By-负责指定标识符值的参与者角色（这可能不同于为协议构造执行填充函数的参与者）。
Table 1: Layered Identities
表1：分层标识
These are the most common address-related fields:
以下是最常见的地址相关字段：
RFC5322.From: Set by - Author
RFC5322.发件人：由-作者设置
Names and addresses for Authors of the message content are listed in the From: field.
发件人：字段中列出了邮件内容作者的姓名和地址。
RFC5322.Reply-To: Set by - Author
RFC5322.Reply-To:由作者设置
If a Recipient sends a reply message that would otherwise use the RFC5322.From field addresses in the original message, the addresses in the RFC5322.Reply-To field are used instead. In other words, this field overrides the From: field for responses from Recipients.
如果收件人发送的回复消息将使用原始消息中的RFC5322.From字段地址，则将使用RFC5322.reply-To字段中的地址。换句话说，对于收件人的响应，此字段将覆盖“发件人：”字段。
RFC5322.Sender: Set by - Originator
RFC5322.发送方：设置人-发起人
This field specifies the address responsible for submitting the message to the transfer service. This field can be omitted if it contains the same address as RFC5322.From. However, omitting this field does not mean that no Sender is specified; it means that that header field is virtual and that the address in the From: field is to be used.
此字段指定负责将邮件提交到传输服务的地址。如果该字段包含与RFC5322.From相同的地址，则可以省略该字段。但是，省略此字段并不意味着未指定发件人；这意味着该头字段是虚拟的，并且要使用From:字段中的地址。
Specification of the notifications Return Addresses, which are contained in RFC5321.MailFrom, is made by the RFC5322.Sender. Typically, the Return address is the same as the Sender address. However, some usage scenarios require it to be different.
RFC5321.MailFrom中包含的通知返回地址由RFC5322.Sender指定。通常，返回地址与发件人地址相同。但是，某些使用场景要求它有所不同。
RFC5322.To/.CC: Set by - Author
RFC5322.To/.CC: Set by - Author
These fields specify MUA Recipient addresses. However, some or all of the addresses in these fields might not be present in the RFC5321.RcptTo commands.
这些字段指定MUA收件人地址。但是，RFC5321.RcptTo命令中可能不存在这些字段中的部分或全部地址。
The distinction between To and CC is subjective. Generally, a To addressee is considered primary and is expected to take action on the message. A CC addressee typically receives a copy as a courtesy.
To和CC之间的区别是主观的。一般来说，收件人被认为是主要的，并期望对邮件采取行动。抄送收件人通常会收到一份副本作为礼节。
RFC5322.BCC: Set by - Author
RFC5322.BCC:由-作者设置
A copy of the message might be sent to an addressee whose participation is not to be disclosed to the RFC5322.To or RFC5322.CC Recipients and, usually, not to the other BCC Recipients. The BCC: header field indicates a message copy to such a Recipient. Use of this field is discussed in [RFC5322].
邮件副本可能会发送给收件人，其参与情况不会透露给RFC5322.to或RFC5322.CC收件人，通常不会透露给其他密件抄送收件人。“密件抄送：邮件头”字段表示发送给此类收件人的邮件副本。[RFC5322]中讨论了此字段的使用。
RFC5321.HELO/.EHLO: Set by - Originator, MSA, MTA
RFC5321.HELO/.EHLO: Set by - Originator, MSA, MTA
Any SMTP client -- including Originator, MSA, or MTA -- can specify its hosting domain identity for the SMTP HELO or EHLO command operation.
任何SMTP客户端（包括发起者、MSA或MTA）都可以为SMTP HELO或EHLO命令操作指定其托管域标识。
RFC3461.ENVID: Set by - Originator
RFC3461.ENVID：设置人-发起人
The MSA can specify an opaque string, to be included in a DSN, as a means of assisting the Return Address Recipient in identifying the message that produced a DSN or message tracking.
MSA可以指定要包含在DSN中的不透明字符串，作为帮助返回地址接收者识别产生DSN或消息跟踪的消息的手段。
RFC5321.MailFrom: Set by - Originator
RFC5321.MailFrom:设置人-发起人
This field is an end-to-end string that specifies an email address for receiving return control information, such as returned messages. The name of this field is misleading, because it is not required to specify either the Author or the Actor responsible for submitting the message. Rather, the Actor responsible for submission specifies the RFC5321.MailFrom address. Ultimately, the simple basis for deciding which address needs to be in the RFC5321.MailFrom field is to determine which address is to be informed about transfer-level problems (and possibly successes).
此字段是一个端到端字符串，指定用于接收返回控制信息（如返回的消息）的电子邮件地址。此字段的名称具有误导性，因为它不需要指定负责提交消息的作者或参与者。相反，负责提交的参与者指定RFC5321.MailFrom地址。最终，决定RFC5321.MailFrom字段中需要哪个地址的简单基础是确定要通知哪个地址有关传输级别的问题（以及可能的成功）。
RFC5321.RcptTo: Set by - Author, Final MTA, MDA
RFC5321.RcptTo：由作者设置，最终MTA，MDA
This field specifies the MUA mailbox address of a Recipient. The string might not be visible in the message content header. For example, the IMF destination address header fields, such as RFC5322.To, might specify a Mailing List mailbox, while the RFC5321.RcptTo address specifies a member of that list.
此字段指定收件人的MUA邮箱地址。该字符串在消息内容标头中可能不可见。例如，IMF目标地址标头字段（如RFC5322.To）可能指定邮件列表邮箱，而RFC5321.RcptTo地址指定该列表的成员。
RFC5321.ORCPT: Set by - Originator.
RFC5321.ORCPT:由-发起人设置。
This is an optional parameter to the RCPT command, indicating the original address to which the current RCPT TO address corresponds, after a mapping was performed during transit. An ORCPT is the only reliable way to correlate a DSN from a multi-Recipient message transfer with the intended Recipient.
这是RCPT命令的可选参数，指示在传输期间执行映射后，当前RCPT到地址对应的原始地址。ORCPT是将多收件人消息传输的DSN与预期收件人关联起来的唯一可靠方法。
RFC5321.Received: Set by - Originator, Relay, Mediator, Dest
RFC5321.接收：设置人-发起人、中继、调解人、目的地
This field contains trace information, including originating host, Relays, Mediators, and MSA host domain names and/or IP Addresses.
此字段包含跟踪信息，包括原始主机、中继、中介和MSA主机域名和/或IP地址。
RFC5321.Return-Path: Set by - Originator
RFC5321.Return-Path：由发起人设置
The MDA records the RFC5321.MailFrom address into the RFC5321.Return-Path field.
MDA将RFC5321.MailFrom地址记录到RFC5321.Return-Path字段中。
RFC2919.List-Id: Set by - Mediator, Author
RFC2919.List-Id:设置人-调解人，作者
This field provides a globally unique Mailing List naming framework that is independent of particular hosts [RFC2919].
此字段提供一个独立于特定主机的全局唯一邮件列表命名框架[RFC2919]。
The identifier is in the form of a domain name; however, the string usually is constructed by combining the two parts of an email address. The result is rarely a true domain name, listed in the domain name service, although it can be.
标识符采用域名的形式；但是，字符串通常由电子邮件地址的两部分组合而成。结果很少是一个真正的域名，在域名服务中列出，尽管它可以是。
RFC2369.List-*: Set by - Mediator, Author
RFC2369.List-*: Set by - Mediator, Author
[RFC2369] defines a collection of message header fields for use by Mailing Lists. In effect, they supply list-specific parameters for common Mailing-List user operations. The identifiers for these operations are for the list itself and the user-as-subscriber [RFC2369].
[RFC2369]定义邮件列表使用的邮件标题字段集合。实际上，它们为常见的邮件列表用户操作提供特定于列表的参数。这些操作的标识符用于列表本身和作为订户的用户[RFC2369]。
RFC0791.SourceAddr: Set by - The Client SMTP sending host immediately preceding the current receiving SMTP server
RFC0791.SourceAddr:设置者-当前接收SMTP服务器之前的客户端SMTP发送主机
[RFC0791] defines the basic unit of data transfer for the Internet: the IP datagram. It contains a Source Address field that specifies the IP Address for the host (interface) from which the datagram was sent. This information is set and provided by the IP layer, which makes it independent of mail-level mechanisms. As such, it is often taken to be authoritative, although it is possible to provide false addresses.
[RFC0791]定义了互联网数据传输的基本单位：IP数据报。它包含一个源地址字段，用于指定发送数据报的主机（接口）的IP地址。该信息由IP层设置和提供，这使得它独立于邮件级别的机制。因此，它通常被认为是权威的，尽管它可能提供虚假地址。
Interactions at the user level entail protocol exchanges, distinct from those that occur at lower layers of the Internet Mail MHS architecture that is, in turn, above the Internet Transport layer. Because the motivation for email, and much of its use, is for interaction among people, the nature and details of these protocol exchanges often are determined by the needs of interpersonal and group communication. To accommodate the idiosyncratic behavior inherent in such communication, only subjective guidelines, rather than strict rules, can be offered for some aspects of system behavior. Mailing Lists provide particularly salient examples.
用户级的交互需要协议交换，这与发生在Internet邮件MHS体系结构较低层（即Internet传输层之上）的交互不同。因为电子邮件的动机，以及它的大部分用途，是为了人与人之间的互动，这些协议交换的性质和细节通常由人际和群体交流的需要决定。为了适应这种交流中固有的特殊行为，只能为系统行为的某些方面提供主观指导，而不是严格的规则。邮件列表提供了特别突出的例子。
A Message User Agent (MUA) works on behalf of User Actors and User applications. It is their representative within the email service.
消息用户代理（MUA）代表用户参与者和用户应用程序工作。这是他们在电子邮件服务中的代表。
The Author MUA (aMUA) creates a message and performs initial submission into the transfer infrastructure via a Mail Submission Agent (MSA). It can also perform any creation- and posting-time archiving in its Message Store (aMS). An MUA aMS can organize messages in many different ways. A common model uses aggregations, called "folders"; in IMAP they are called "mailboxes". This model
作者MUA（aMUA）创建一条消息，并通过邮件提交代理（MSA）向传输基础设施执行初始提交。它还可以在其消息存储（aMS）中执行任何创建和发布时间存档。MUA aMS可以以多种不同的方式组织消息。通用模型使用聚合，称为“文件夹”；在IMAP中，它们被称为“邮箱”。这个模型
allows a folder for messages under development (Drafts), a folder for messages waiting to be sent (Queued or Unsent), and a folder for messages that have been successfully posted for transfer (Sent). But none of these folders is required. For example, IMAP allows drafts to be stored in any folder, so no Drafts folder needs to be present.
允许为正在开发的邮件（草稿）创建文件夹，为等待发送的邮件创建文件夹（排队或未发送），为已成功投递以进行传输的邮件创建文件夹（已发送）。但这些文件夹都不是必需的。例如，IMAP允许草稿存储在任何文件夹中，因此不需要存在草稿文件夹。
The Recipient MUA (rMUA) works on behalf of the Recipient to process received mail. This processing includes generating user-level disposition control messages, displaying and disposing of the received message, and closing or expanding the user-communication loop by initiating replies and forwarding new messages.
收件人MUA（rMUA）代表收件人处理收到的邮件。该处理包括生成用户级处置控制消息、显示和处置接收到的消息，以及通过发起应答和转发新消息来关闭或扩展用户通信循环。
NOTE: Although not shown in Figure 5, an MUA itself can have a distributed implementation, such as a "thin" user-interface module on a constrained device such as a smartphone, with most of the MUA functionality running remotely on a more capable server. An example of such an architecture might use IMAP [RFC3501] for most of the interactions between an MUA client and an MUA server. An approach for such scenarios is defined by [RFC4550].
注意：尽管图5中未显示，但MUA本身可以具有分布式实现，如智能手机等受约束设备上的“瘦”用户界面模块，大部分MUA功能可以在功能更强的服务器上远程运行。这种体系结构的一个示例可以将IMAP[RFC3501]用于MUA客户端和MUA服务器之间的大多数交互。[RFC4550]定义了此类场景的方法。
A Mediator is a special class of MUA. It performs message re-posting, as discussed in Section 2.1.
调解人是MUA的一个特殊类别。如第2.1节所述，它执行消息重新发布。
An MUA can be automated, on behalf of a User who is not present at the time the MUA is active. One example is a bulk sending service that has a timed-initiation feature. These services are not to be confused with a Mailing List Mediator, since there is no incoming message triggering the activity of the automated service.
MUA可以代表MUA激活时不在场的用户进行自动化。一个示例是具有定时启动功能的批量发送服务。不要将这些服务与邮件列表中介混淆，因为没有触发自动服务活动的传入消息。
A popular and problematic MUA is an automatic responder, such as one that sends out-of-office notices. This behavior might be confused with that of a Mediator, but this MUA is generating a new message. Automatic responders can annoy Users of Mailing Lists unless they follow [RFC3834].
一种流行且有问题的MUA是一种自动响应程序，例如发送离职通知的程序。这种行为可能与中介的行为相混淆，但这种MUA正在生成一条新消息。自动回复者可能会骚扰邮件列表的用户，除非他们遵循[RFC3834]。
The identity fields are relevant to a typical MUA:
标识字段与典型的MUA相关：
RFC5322.From
RFC5322.来自
RFC5322.Reply-To
RFC5322.答复
RFC5322.Sender
RFC5322.发送器
RFC5322.To, RFC5322.CC
RFC5322.To，RFC5322.CC
RFC5322.BCC
RFC5322.BCC
An MUA can employ a long-term Message Store (MS). Figure 5 depicts an Author's MS (aMS) and a Recipient's MS (rMS). An MS can be located on a remote server or on the same machine as the MUA.
MUA可以使用长期消息存储（MS）。图5描述了作者的MS（aMS）和接收者的MS（rMS）。MS可以位于远程服务器上，也可以与MUA位于同一台机器上。
An MS acquires messages from an MDA either proactively by a local mechanism or even by a standardized mechanism such as SMTP(!), or reactively by using POP or IMAP. The MUA accesses the MS either by a local mechanism or by using POP or IMAP. Using POP for individual message accesses, rather than for bulk transfer, is relatively rare and inefficient.
MS通过本地机制或甚至通过标准化机制（如SMTP（！）从MDA主动获取消息，或使用POP或IMAP被动获取消息。MUA通过本地机制或使用POP或IMAP访问MS。将POP用于单独的消息访问，而不是批量传输，这相对较少且效率低下。
A Mail Submission Agent (MSA) accepts the message submitted by the aMUA and enforces the policies of the hosting ADMD and the requirements of Internet standards. An MSA represents an unusual functional dichotomy. It represents the interests of the Author (aMUA) during message posting, to facilitate posting success; it also represents the interests of the MHS. In the architecture, these responsibilities are modeled, as shown in Figure 5, by dividing the MSA into two sub-components, aMSA and hMSA, respectively. Transfer of responsibility for a single message, from an Author's environment to the MHS, is called "posting". In Figure 5, it is marked as the (S) transition, within the MSA.
邮件提交代理（MSA）接受aMUA提交的邮件，并执行托管ADMD的策略和互联网标准的要求。MSA代表一种不寻常的功能二分法。它代表了作者（aMUA）在信息发布期间的利益，以促进发布成功；它也代表了MHS的利益。在架构中，通过将MSA分别划分为两个子组件aMSA和hMSA，对这些职责进行建模，如图5所示。将单个消息的责任从作者的环境转移到MHS，称为“发布”。在图5中，它被标记为MSA中的（S）转换。
The hMSA takes transit responsibility for a message that conforms to the relevant Internet standards and to local site policies. It rejects messages that are not in conformance. The MSA performs final message preparation for submission and effects the transfer of responsibility to the MHS, via the hMSA. The amount of preparation depends upon the local implementations. Examples of aMSA tasks include adding header fields, such as Date: and Message-ID:, and modifying portions of the message from local notations to Internet standards, such as expanding an address to its formal IMF representation.
hMSA负责传输符合相关互联网标准和当地网站政策的信息。它拒绝不一致的消息。MSA通过hMSA执行提交的最终信息准备，并将责任转移至MHS。准备的数量取决于本地实现。aMSA任务的示例包括添加标题字段，例如日期：和消息ID:，以及将消息的某些部分从本地符号修改为Internet标准，例如将地址扩展为其正式的IMF表示形式。
Historically, standards-based MUA/MSA message postings have used SMTP [RFC5321]. The standard currently preferred is SUBMISSION [RFC4409]. Although SUBMISSION derives from SMTP, it uses a separate TCP port and imposes distinct requirements, such as access authorization.
历史上，基于标准的MUA/MSA邮件发布使用SMTP[RFC5321]。目前首选的标准是提交[RFC4409]。尽管提交源于SMTP，但它使用一个单独的TCP端口，并提出了不同的要求，例如访问授权。
These identities are relevant to the MSA:
这些身份与MSA相关：
RFC5321.HELO/.EHLO
RFC5321.HELO/.EHLO
RFC3461.ENVID
RFC3461.ENVID
RFC5321.MailFrom
RFC5321.MailFrom
RFC5321.RcptTo
RFC5321.RcptTo
RFC5321.Received
RFC5321.已收到
RFC0791.SourceAddr
RFC0791.SourceAddr
A Message Transfer Agent (MTA) relays mail for one application-level "hop". It is like a packet switch or IP router in that its job is to make routing assessments and to move the message closer to the Recipients. Of course, email objects are typically much larger than the payload of a packet or datagram, and the end-to-end latencies are typically much higher. Relaying is performed by a sequence of MTAs until the message reaches a destination MDA. Hence, an MTA implements both client and server MTA functionality; it does not change addresses in the envelope or reformulate the editorial content. A change in data form, such as to MIME Content-Transfer-Encoding, is within the purview of an MTA, but removal or replacement of body content is not. An MTA also adds trace information [RFC2505].
消息传输代理（MTA）为一个应用程序级别的“跃点”中继邮件。它就像一个分组交换机或IP路由器，它的工作是进行路由评估，并将消息移近收件人。当然，电子邮件对象通常比数据包或数据报的有效负载大得多，并且端到端延迟通常要高得多。中继由一系列MTA执行，直到消息到达目标MDA。因此，MTA同时实现客户端和服务器MTA功能；它不会更改信封中的地址或重新编排编辑内容。数据格式的更改（如MIME内容传输编码）属于MTA的权限范围，但正文内容的删除或替换不属于MTA的权限范围。MTA还添加跟踪信息[RFC2505]。
NOTE: Within a destination ADMD, email-relaying modules can make a variety of changes to the message, prior to delivery. In such cases, these modules are acting as Gateways, rather than MTAs.
注意：在目标ADMD中，电子邮件中继模块可以在发送之前对邮件进行各种更改。在这种情况下，这些模块充当网关，而不是MTA。
Internet Mail uses SMTP ([RFC5321], [RFC2821], [RFC0821]) primarily to effect point-to-point transfers between peer MTAs. Other transfer mechanisms include Batch SMTP [RFC2442] and On-Demand Mail Relay (ODMR) SMTP [RFC2645]. As with most network-layer mechanisms, the Internet Mail SMTP supports a basic level of reliability, by virtue of providing for retransmission after a temporary transfer failure. Unlike typical packet switches (and Instant Messaging services), Internet Mail MTAs are expected to store messages in a manner that allows recovery across service interruptions, such as host-system shutdown. The degree of such robustness and persistence by an MTA can vary. The base SMTP specification provides a framework for protocol response codes. An extensible enhancement to this framework is defined in [RFC5248].
Internet Mail使用SMTP（[RFC5321]、[RFC2821]、[RFC0821]）主要用于在对等MTA之间进行点对点传输。其他传输机制包括批处理SMTP[RFC2442]和按需邮件中继（ODMR）SMTP[RFC2645]。与大多数网络层机制一样，Internet邮件SMTP通过在临时传输失败后提供重新传输，支持基本级别的可靠性。与典型的分组交换机（和即时消息服务）不同，Internet Mail MTA存储消息的方式应允许跨服务中断（如主机系统关闭）进行恢复。MTA的这种健壮性和持久性的程度可能会有所不同。基本SMTP规范为协议响应代码提供了一个框架。[RFC5248]中定义了对该框架的可扩展增强。
Although quite basic, the dominant routing mechanism for Internet Mail is the DNS MX record [RFC1035], which specifies an MTA through which the queried domain can be reached. This mechanism presumes a public, or at least a common, backbone that permits any attached MTA to connect to any other.
虽然非常基本，但Internet邮件的主要路由机制是DNS MX记录[RFC1035]，它指定一个MTA，通过该MTA可以访问查询的域。这种机制假定有一个公共主干网，或者至少是一个公共主干网，允许任何连接的MTA连接到任何其他主干网。
MTAs can perform any of these well-established roles:
MTA可以执行以下任何既定角色：
Boundary MTA: An MTA that is part of an ADMD and interacts with MTAs in other ADMDs. This is also called a Border MTA. There can be different Boundary MTAs, according to the direction of mail-flow.
边界MTA：作为ADMD一部分并与其他ADMD中的MTA交互的MTA。这也称为边界MTA。根据邮件流的方向，可以有不同的边界MTA。
Outbound MTA: An MTA that relays messages to other ADMDs.
出站MTA：将邮件中继到其他ADMD的MTA。
Inbound MTA: An MTA that receives inbound SMTP messages from MTA Relays in other ADMDs, for example, an MTA running on the host listed as the target of an MX record.
入站MTA：从其他ADMD中的MTA中继接收入站SMTP邮件的MTA，例如，在列为MX记录目标的主机上运行的MTA。
Final MTA: The MTA that transfers a message to the MDA.
最终MTA：将消息传输到MDA的MTA。
These identities are relevant to the MTA:
这些身份与MTA相关：
RFC5321.HELO/.EHLO
RFC5321.HELO/.EHLO
RFC3461.ENVID
RFC3461.ENVID
RFC5321.MailFrom
RFC5321.MailFrom
RFC5321.RcptTo
RFC5321.RcptTo
RFC5322.Received: Set by - Relay Server
RFC5322.接收：由中继服务器设置
RFC0791.SourceAddr
RFC0791.SourceAddr
A transfer of responsibility from the MHS to a Recipient's environment (mailbox) is called "delivery". In the architecture, as depicted in Figure 5, delivery takes place within a Mail Delivery Agent (MDA) and is shown as the (D) transition from the MHS-oriented MDA component (hMDA) to the Recipient-oriented MDA component (rMDA).
将责任从MHS转移到收件人的环境（邮箱）称为“交付”。在该体系结构中，如图5所示，传递在邮件传递代理（MDA）中进行，并显示为（D）从面向MHS的MDA组件（hMDA）到面向收件人的MDA组件（rMDA）的转换。
An MDA can provide distinctive, address-based functionality, made possible by its detailed information about the properties of the destination address. This information might also be present elsewhere in the Recipient's ADMD, such as at an organizational border (Boundary) Relay. However, it is required for the MDA, if only because the MDA is required to know where to deliver the message.
MDA可以提供独特的、基于地址的功能，这是通过其有关目标地址属性的详细信息实现的。此信息也可能存在于收件人的ADMD中的其他位置，例如在组织边界（Boundary）中继处。但是，MDA需要它，因为MDA需要知道在哪里传递消息。
Like an MSA, an MDA serves two roles, as depicted in Figure 5. Formal transfer of responsibility, called "delivery", is effected between the two components that embody these roles and is shown as "(D)" in Figure 5. The MHS portion (hMDA) primarily functions as a server SMTP engine. A common additional role is to redirect the message to an alternative address, as specified by the Recipient addressee's preferences. The job of the Recipient portion of the MDA (rMDA) is to perform any delivery actions that the Recipient specifies.
与MSA一样，MDA有两个角色，如图5所示。正式的责任转移称为“交付”，在体现这些角色的两个组成部分之间进行，如图5中的“（D）”所示。MHS部分（hMDA）主要用作服务器SMTP引擎。一个常见的附加角色是将邮件重定向到收件人首选项指定的替代地址。MDA（rMDA）的接收方部分的工作是执行接收方指定的任何交付操作。
Transfer into the MDA is accomplished by a normal MTA transfer mechanism. Transfer from an MDA to an MS uses an access protocol, such as POP or IMAP.
传输到MDA是通过正常的MTA传输机制完成的。从MDA到MS的传输使用访问协议，如POP或IMAP。
NOTE: The term "delivery" can refer to the formal, MHS function specified here or to the first time a message is displayed to a Recipient. A simple, practical test for whether the MHS-based definition applies is whether a DSN can be generated.
注：术语“传递”可以指此处指定的正式MHS功能，也可以指首次向收件人显示邮件时的功能。对于基于MHS的定义是否适用，一个简单实用的测试是是否可以生成DSN。
These identities are relevant to the MDA:
这些标识与MDA相关：
RFC5321.Return-Path: Set by - Author Originator or Mediator Originator
RFC5321.Return-Path：由-作者发起人或中介发起人设置
The MDA records the RFC5321.MailFrom address into the RFC5321.Return-Path field.
MDA将RFC5321.MailFrom地址记录到RFC5321.Return-Path字段中。
RFC5322.Received: Set by - MDA server
RFC5322.已接收：由-MDA服务器设置
An MDA can record a Received: header field to indicate trace information, including source host and receiving host domain names and/or IP Addresses.
MDA可以记录Received:头字段以指示跟踪信息，包括源主机和接收主机域名和/或IP地址。
From the origination site to the point of delivery, Internet Mail usually follows a "push" model. That is, the Actor that holds the message initiates transfer to the next venue, typically with SMTP [RFC5321] or the Local Mail Transfer Protocol (LMTP) [RFC2033]. With a "pull" model, the Actor that holds the message waits for the Actor
从发起站点到交付点，互联网邮件通常遵循“推送”模式。也就是说，持有消息的参与者通常使用SMTP[RFC5321]或本地邮件传输协议（LMTP）[RFC2033]发起到下一个地点的传输。对于“拉”模型，持有消息的参与者等待参与者
in the next venue to initiate a request for transfer. Standardized mechanisms for pull-based MHS transfer are ETRN [RFC1985] and ODMR [RFC2645].
在下一个场地发起换乘请求。基于拉动的MHS传输的标准化机制是ETRN[RFC1985]和ODMR[RFC2645]。
After delivery, the Recipient's MUA (or MS) can gain access by having the message pushed to it or by having the receiver of access pull the message, such as by using POP [RFC1939] and IMAP [RFC3501].
交付后，接收方的MUA（或MS）可以通过将消息推送到其上或通过让访问接收方拉取消息（例如通过使用POP[RFC1939]和IMAP[RFC3501]）来获得访问权。
A discussion of any interesting system architecture often bogs down when architecture and implementation are confused. An architecture defines the conceptual functions of a service, divided into discrete conceptual modules. An implementation of that architecture can combine or separate architectural components, as needed for a particular operational environment. For example, a software system that primarily performs message relaying is an MTA, yet it might also include MDA functionality. That same MTA system might be able to interface with non-Internet email services and thus perform both as an MTA and as a Gateway.
当体系结构和实现混淆时，对任何有趣的系统体系结构的讨论往往会陷入困境。体系结构定义了服务的概念性功能，将其划分为离散的概念性模块。该体系结构的实现可以根据特定操作环境的需要组合或分离体系结构组件。例如，主要执行消息中继的软件系统是MTA，但也可能包括MDA功能。同一个MTA系统可能能够与非Internet电子邮件服务交互，从而同时作为MTA和网关运行。
Similarly, implemented modules might be configured to form elaborations of the architecture. An interesting example is a distributed MS. One portion might be a remote server and another might be local to the MUA. As discussed in [RFC1733], there are three operational relationships among such MSs:
类似地，可以配置实现的模块以形成架构的详细说明。一个有趣的例子是分布式MS。一部分可能是远程服务器，另一部分可能是MUA的本地服务器。如[RFC1733]所述，此类MSs之间存在三种操作关系：
Online: The MS is remote, and messages are accessible only when the MUA is attached to the MS so that the MUA will re-fetch all or part of a message from one session to the next.
联机：MS是远程的，只有当MUA连接到MS时，才能访问消息，以便MUA从一个会话到下一个会话重新获取全部或部分消息。
Offline: The MS is local to the User, and messages are completely moved from any remote store, rather than (also) being retained there.
离线：MS是用户本地的，消息完全从任何远程存储移动，而不是（也）保留在那里。
Disconnected: An rMS and a uMS are kept synchronized, for all or part of their contents, while they are connected. When they are disconnected, mail can arrive at the rMS and the User can make changes to the uMS. The two stores are re-synchronized when they are reconnected.
断开连接：rMS和uMS在连接时，其全部或部分内容保持同步。断开连接后，邮件可以到达rMS，用户可以对uMS进行更改。这两个存储在重新连接时会重新同步。
Basic message transfer from Author to Recipients is accomplished by using an asynchronous store-and-forward communication infrastructure in a sequence of independent transmissions through some number of MTAs. A very different task is a sequence of postings and deliveries through Mediators. A Mediator forwards a message through a
从作者到收件人的基本消息传输是通过使用异步存储转发通信基础设施，通过一定数量的MTA以独立传输的顺序完成的。一个非常不同的任务是通过调解人发布和交付的序列。调解人通过电子邮件转发消息
re-posting process. The Mediator shares some functionality with basic MTA relaying, but has greater flexibility in both addressing and content than is available to MTAs.
重新发布流程。Mediator与基本MTA中继共享一些功能，但在寻址和内容方面比MTA具有更大的灵活性。
This is the core set of message information that is commonly set by all types of Mediators:
这是消息信息的核心集，通常由所有类型的中介设置：
RFC5321.HELO/.EHLO: Set by - Mediator Originator
RFC5321.HELO/.EHLO: Set by - Mediator Originator
RFC3461.ENVID: Set by - Mediator Originator
RFC3461.ENVID:由-调解人发起人设置
RFC5321.RcptTo: Set by - Mediator Author
RFC5321.RcptTo:由-中介作者设置
RFC5321.Received: Set by - Mediator Dest
RFC5321.已接收：由-Mediator Dest设置
The Mediator can record received information to indicate the delivery to the original address and submission to the alias address. The trace of Received: header fields can include everything from original posting, through relaying, to final delivery.
调解人可以记录收到的信息，以指示发送到原始地址和提交到别名地址。接收：标题字段的跟踪可以包括从原始过账、中继到最终交付的所有内容。
The aspect of a Mediator that distinguishes it from any other MUA creating a message is that a Mediator preserves the integrity and tone of the original message, including the essential aspects of its origination information. The Mediator might also add commentary.
中介与创建消息的任何其他MUA的区别在于，中介保持原始消息的完整性和基调，包括其原始信息的基本方面。调解人也可以添加评论。
Examples of MUA messages that a Mediator does not create include:
调解人不创建的MUA消息示例包括：
New message that forwards an existing message:
转发现有邮件的新邮件：
Although this action provides a basic template for a class of Mediators, its typical occurrence is not, itself, an example of a Mediator. The new message is viewed as being from the Actor that is doing the forwarding, rather than from the original Author. A new message encapsulates the original message and is seen as from the new Originator. This Mediator Originator might add commentary and can modify the original message content. Because the forwarded message is a component of the message sent by the new Originator, the new message creates a new dialogue. However, the final Recipient still sees the contained message as from the original Author.
尽管此操作为一类中介提供了一个基本模板，但它的典型出现本身并不是中介的示例。新消息被视为来自进行转发的参与者，而不是来自原始作者。新消息封装了原始消息，并被视为来自新的发起人。此中介发起人可能会添加注释，并可以修改原始邮件内容。由于转发的消息是新发起者发送的消息的一个组成部分，因此新消息将创建一个新的对话。但是，最终的接收者仍然认为包含的消息来自原始作者。
Reply:
答复:
When a Recipient responds to the Author of a message, the new message is not typically viewed as a forwarding of the original. Its focus is the new content, although it might
当收件人回复邮件作者时，新邮件通常不会被视为原始邮件的转发。它的重点是新内容，尽管它可能
contain all or part of the material from the original message. The earlier material is merely contextual and secondary. This includes automated replies, such as vacation out-of-office notices, as discussed in Section 4.2.1.
包含原始邮件中的全部或部分内容。早期的材料仅仅是上下文和次要的。这包括自动回复，如第4.2.1节所述的休假离开办公室通知。
Annotation:
注释：
The integrity of the original message is usually preserved, but one or more comments about the message are added in a manner that distinguishes commentary from original text. The primary purpose of the new message is to provide commentary from a new Author, similar to a Reply.
通常保留原始消息的完整性，但添加一条或多条有关消息的注释时，应将注释与原始文本区分开来。新消息的主要目的是提供新作者的评论，类似于回复。
The remainder of this section describes common examples of Mediators.
本节的其余部分将介绍中介的常见示例。
One function of an MDA is to determine the internal location of a mailbox in order to perform delivery. An Alias is a simple re-addressing facility that provides one or more new Internet Mail addresses, rather than a single, internal one; the message continues through the transfer service, for delivery to one or more alternate addresses. Although typically implemented as part of an MDA, this facility is a Recipient function. It resubmits the message, although all handling information except the envelope Recipient (rfc5321.RcptTo) address is retained. In particular, the Return Address (rfc5321.MailFrom) is unchanged.
MDA的一个功能是确定邮箱的内部位置以执行传递。别名是一种简单的重新寻址功能，它提供一个或多个新的Internet邮件地址，而不是单个内部地址；该消息通过传输服务继续发送到一个或多个备用地址。虽然通常作为MDA的一部分实现，但此功能是一个接收方功能。它重新提交邮件，但保留信封收件人（rfc5321.RcptTo）地址以外的所有处理信息。特别是，返回地址（rfc5321.MailFrom）保持不变。
What is distinctive about this forwarding mechanism is how closely it resembles normal MTA store-and-forward relaying. Its only significant difference is that it changes the RFC5321.RcptTo value. Because this change is so small, aliasing can be viewed as a part of the lower-level mail-relaying activity. However, this small change has a large semantic impact: The designated Recipient has chosen a new Recipient.
这种转发机制的独特之处在于它与正常的MTA存储和转发中继非常相似。它唯一的显著区别是改变了RFC5321.RcptTo值。由于此更改非常小，因此可以将别名视为较低级别邮件中继活动的一部分。然而，这个小小的变化有很大的语义影响：指定的接收者选择了一个新的接收者。
NOTE: When the replacement list includes more than one address, the alias is increasingly likely to have delivery problems. Any problem reports go to the original Author, not the administrator of the alias entry. This makes it more difficult to resolve the problem, because the original Author has no knowledge of the Alias mechanism.
注意：当替换列表包含多个地址时，别名越来越可能出现传递问题。任何问题报告都将提交给原始作者，而不是别名条目的管理员。这使得解决问题更加困难，因为原始作者不了解别名机制。
Including the core set of message information listed at the beginning of this section, Alias typically changes:
包括本节开头列出的核心消息信息集，Alias通常会更改：
RFC5322.To/.CC/.BCC: Set by - Author
RFC5322.To/.CC/.BCC: Set by - Author
These fields retain their original addresses.
这些字段保留其原始地址。
RFC5321.MailFrom: Set by - Author
RFC5321.MailFrom:设置人-作者
The benefit of retaining the original MailFrom value is to ensure that an Actor related to the originating ADMD knows there has been a delivery problem. On the other hand, the responsibility for handling problems, when transiting from the original Recipient mailbox to the alias mailbox usually lies with that original Recipient, because the Alias mechanism is strictly under that Recipient's control. Retaining the original MailFrom address prevents this.
保留原始MailFrom值的好处是确保与原始ADMD相关的参与者知道存在传递问题。另一方面，当从原始收件人邮箱转换到别名邮箱时，处理问题的责任通常由该原始收件人承担，因为别名机制严格受该收件人的控制。保留原始MailFrom地址可防止出现这种情况。
Also called the ReDirector, the ReSender's actions differ from forwarding because the Mediator "splices" a message's addressing information to connect the Author of the original message with the Recipient of the new message. This connection permits them to have direct exchange, using their normal MUA Reply functions, while also recording full reference information about the Recipient who served as a Mediator. Hence, the new Recipient sees the message as being from the original Author, even if the Mediator adds commentary.
也称为重定向器，重新发送的操作与转发不同，因为中介器“拼接”消息的寻址信息，以将原始消息的作者与新消息的收件人连接起来。这种连接允许他们使用正常的MUA回复功能进行直接交换，同时还记录作为调解人的收件人的完整参考信息。因此，即使调解人添加了注释，新接收人也会将消息视为来自原始作者。
Including the core set of message information listed at the beginning of this section, these identities are relevant to a resent message:
包括本节开头列出的核心消息信息集，这些标识与重新发送的消息相关：
RFC5322.From: Set by - original Author
RFC5322.发件人：设置人-原始作者
Names and addresses for the original Author of the message content are retained. The free-form (display-name) portion of the address might be modified to provide an informal reference to the ReSender.
保留邮件内容的原始作者的姓名和地址。地址的自由格式（显示名称）部分可能会被修改，以提供对重发者的非正式引用。
RFC5322.Reply-To: Set by - original Author
RFC5322.回复：由原始作者设置
If this field is present in the original message, it is retained in the resent message.
如果原始邮件中存在此字段，则它将保留在重新发送邮件中。
RFC5322.Sender: Set by - Author's Originator or Mediator Originator
RFC5322.发送方：由-作者的发起人或调解人发起人设置
RFC5322.To/.CC/.BCC: Set by - original Author
RFC5322.To/.CC/.BCC: Set by - original Author
These fields specify the original message Recipients.
这些字段指定原始邮件收件人。
RFC5322.Resent-From: Set by - Mediator Author
RFC5322.Resent-From:由-中介作者设置
This address is of the original Recipient who is redirecting the message. Otherwise, the same rules apply to the Resent-From: field as to an original RFC5322.From field.
此地址是重定向邮件的原始收件人的地址。否则，与原始RFC5322.From字段相同的规则适用于Recent From:字段。
RFC5322.Resent-Sender: Set by - Mediator Originator
RFC5322.Resent-Sender:由-中介发起人设置
The address of the Actor responsible for resubmitting the message. As with RFC5322.Sender, this field can be omitted when it contains the same address as RFC5322.Resent-From.
负责重新提交邮件的参与者的地址。与RFC5322.Sender一样，如果此字段包含与RFC5322.Recent-From相同的地址，则可以忽略此字段。
RFC5322.Resent-To/-CC/-BCC: Set by - Mediator Author
RFC5322.Resent-To/-CC/-BCC: Set by - Mediator Author
The addresses of the new Recipients who are now able to reply to the original Author.
现在可以回复原作者的新收件人的地址。
RFC5321.MailFrom: Set by - Mediator Originator
RFC5321.MailFrom:设置人-中介发起人
The Actor responsible for resubmission (RFC5322.Resent-Sender) is also responsible for specifying the new MailFrom address.
负责重新提交的参与者（RFC5322.Recent Sender）还负责指定新的MailFrom地址。
A Mailing List receives messages as an explicit addressee and then re-posts them to a list of subscribed members. The Mailing List performs a task that can be viewed as an elaboration of the ReSender. In addition to sending the new message to a potentially large number of new Recipients, the Mailing List can modify content, for example, by deleting attachments, converting the format, and adding list-specific comments. Mailing Lists also archive messages posted by Authors. Still the message retains characteristics of being from the original Author.
邮件列表以显式收件人的身份接收消息，然后将其重新发布到已订阅成员的列表中。邮件列表执行的任务可以看作是重新发送的详细说明。除了向潜在的大量新收件人发送新邮件外，邮件列表还可以修改内容，例如，通过删除附件、转换格式和添加特定于列表的注释。邮件列表还存档作者发布的邮件。尽管如此，这条信息仍然保留了原作者的特征。
Including the core set of message information listed at the beginning of this section, these identities are relevant to a Mailing List processor when submitting a message:
包括本节开头列出的核心邮件信息集，这些标识在提交邮件时与邮件列表处理程序相关：
RFC2919.List-Id: Set by - Mediator Author
RFC2919.List-Id:设置人-中介作者
RFC2369.List-*: Set by - Mediator Author
RFC2369.List-*: Set by - Mediator Author
RFC5322.From: Set by - original Author
RFC5322.发件人：设置人-原始作者
Names and email addresses for the original Author of the message content are retained.
保留邮件内容原始作者的姓名和电子邮件地址。
RFC5322.Reply-To: Set by - Mediator or original Author
RFC5322.Reply-To:由-调解人或原始作者设置
Although problematic, it is common for a Mailing List to assign its own addresses to the Reply-To: header field of messages that it posts. This assignment is intended to ensure that replies go to all list members, rather than to only the original Author. As a User Actor, a Mailing List is the Author of the new message and can legitimately set the Reply-To: value. As a Mediator attempting to represent the message on behalf of its original Author, creating or modifying a Reply-To: field can be viewed as violating that Author's intent. When the Reply-To is modified in this way, a reply that is meant only for the original Author will instead go to the entire list. When the Mailing List does not set the field, a reply meant for the entire list can instead go only to the original Author. At best, either choice is a matter of group culture for the particular list.
虽然有问题，但邮件列表通常会将自己的地址分配给它发布的邮件的Reply to:header字段。此任务旨在确保回复发送给所有列表成员，而不是仅发送给原始作者。作为用户参与者，邮件列表是新消息的作者，可以合法地将Reply设置为：value。作为试图代表原始作者表示消息的调解人，创建或修改Reply to:字段可能会被视为违反该作者的意图。以这种方式修改回复对象时，仅针对原始作者的回复将转到整个列表。当邮件列表未设置字段时，针对整个列表的回复只能发送给原始作者。充其量，这两种选择都是特定列表的群体文化问题。
RFC5322.Sender: Set by - Author Originator or Mediator Originator
RFC5322.发件人：设置人-作者发件人或调解人发件人
This field usually specifies the address of the Actor responsible for Mailing List operations. Mailing Lists that operate in a manner similar to a simple MTA Relay preserve as much of the original handling information as possible, including the original RFC5322.Sender field. (Note that this mode of operation causes the Mailing List to behave much like an Alias, with a possible difference in number of new addressees.)
此字段通常指定负责邮件列表操作的参与者的地址。以类似于简单MTA中继的方式操作的邮件列表尽可能多地保留原始处理信息，包括原始RFC5322.Sender字段。（请注意，此操作模式导致邮件列表的行为与别名非常相似，新收件人的数量可能有所不同。）
RFC5322.To/.CC: Set by - original Author
RFC5322.To/.CC: Set by - original Author
These fields usually contain the original list of Recipient addresses.
这些字段通常包含收件人地址的原始列表。
RFC5321.MailFrom: Set by - Mediator Originator
RFC5321.MailFrom:设置人-中介发起人
Because a Mailing List can modify the content of a message in any way, it is responsible for that content; that is, it is an Author. As such, the Return Address is specified by the Mailing List. Although it is plausible for the Mailing List to reuse the Return Address employed by the original Originator, notifications sent to that address after a message has been processed by a Mailing List could be problematic.
因为邮件列表可以以任何方式修改邮件的内容，所以它对该内容负责；也就是说，它是一个作者。因此，回信地址由邮件列表指定。虽然邮件列表重用原始发起者使用的返回地址是合理的，但邮件列表处理邮件后发送到该地址的通知可能会有问题。
A Gateway performs the basic routing and transfer work of message relaying, but it also is permitted to modify content, structure, address, or attributes as needed to send the message into a messaging environment that operates under different standards or potentially incompatible policies. When a Gateway connects two differing messaging services, its role is easy to identify and understand. When it connects environments that follow similar technical standards, but significantly different administrative policies, it is easy to view a Gateway as merely an MTA.
网关执行消息中继的基本路由和传输工作，但也允许它根据需要修改内容、结构、地址或属性，以便将消息发送到在不同标准或潜在不兼容策略下运行的消息环境中。当网关连接两个不同的消息传递服务时，其角色很容易识别和理解。当它连接遵循类似技术标准但管理策略明显不同的环境时，很容易将网关仅仅视为MTA。
The critical distinction between an MTA and a Gateway is that a Gateway can make substantive changes to a message to map between the standards. In virtually all cases, this mapping results in some degree of semantic loss. The challenge of Gateway design is to minimize this loss. Standardized Gateways to Internet Mail are facsimile [RFC4143], voicemail [RFC3801], and the Multimedia Messaging Service (MMS) [RFC4356].
MTA和网关之间的关键区别在于，网关可以对消息进行实质性更改，以便在标准之间进行映射。在几乎所有情况下，这种映射都会导致一定程度的语义损失。网关设计的挑战是最大限度地减少这种损失。互联网邮件的标准网关是传真[RFC4143]、语音邮件[RFC3801]和彩信服务（MMS）[RFC4356]。
A Gateway can set any identity field available to an MUA. Including the core set of message information listed at the beginning of this section, these identities are typically relevant to Gateways:
网关可以设置MUA可用的任何标识字段。包括本节开头列出的核心消息信息集，这些标识通常与网关相关：
RFC5322.From: Set by - original Author
RFC5322.发件人：设置人-原始作者
Names and addresses for the original Author of the message content are retained. As for all original addressing information in the message, the Gateway can translate addresses as required to continue to be useful in the target environment.
保留邮件内容的原始作者的姓名和地址。对于消息中的所有原始地址信息，网关可以根据需要转换地址，以便在目标环境中继续发挥作用。
RFC5322.Reply-To: Set by - original Author
RFC5322.回复：由原始作者设置
It is best for a Gateway to retain this information, if it is present. The ability to perform a successful reply by a Recipient is a typical test of Gateway functionality.
网关最好保留此信息（如果存在）。由收件人执行成功回复的能力是网关功能的典型测试。
RFC5322.Sender: Set by - Author Originator or Mediator Originator
RFC5322.发件人：设置人-作者发件人或调解人发件人
This field can retain the original value or can be set to a new address.
此字段可以保留原始值，也可以设置为新地址。
RFC5322.To/.CC/.BCC: Set by - original Recipient
RFC5322.To/.CC/.BCC: Set by - original Recipient
These fields usually retain their original addresses.
这些字段通常保留其原始地址。
RFC5321.MailFrom: Set by - Author Originator or Mediator Originator
RFC5321.MailFrom:设置人-作者发起人或调解人发起人
The Actor responsible for handling the message can specify a new address to receive handling notices.
负责处理消息的参与者可以指定接收处理通知的新地址。
To enforce security boundaries, organizations can subject messages to analysis for conformance with its safety policies. An example is detection of content classed as spam or a virus. A filter might alter the content to render it safe, such as by removing content deemed unacceptable. Typically, these actions add content to the message that records the actions.
为了加强安全边界，组织可以对消息进行分析，以确保其符合其安全策略。例如，检测分类为垃圾邮件或病毒的内容。过滤器可能会更改内容以使其安全，例如删除被认为不可接受的内容。通常，这些操作会将内容添加到记录操作的消息中。
This document describes the existing Internet Mail architecture. It introduces no new capabilities. The security considerations of this deployed architecture are documented extensively in the technical specifications referenced by this document. These specifications cover classic security topics, such as authentication and privacy. For example, email-transfer protocols can use standardized mechanisms for operation over authenticated and/or encrypted links, and message content has similar protection standards available. Examples of such mechanisms include SMTP-TLS [RFC3207], SMTP-Auth [RFC4954], OpenPGP [RFC4880], and S/MIME [RFC3851].
本文档描述了现有的Internet邮件体系结构。它没有引入新功能。此部署体系结构的安全注意事项在本文档引用的技术规范中有广泛的记录。这些规范涵盖了经典的安全主题，如身份验证和隐私。例如，电子邮件传输协议可以使用标准化机制在经过身份验证和/或加密的链接上进行操作，并且消息内容具有类似的可用保护标准。此类机制的示例包括SMTP-TLS[RFC3207]、SMTP Auth[RFC4954]、OpenPGP[RFC4880]和S/MIME[RFC3851]。
The core of the Internet Mail architecture does not impose any security requirements or functions on the end-to-end or hop-by-hop components. For example, it does not require participant authentication and does not attempt to prevent data disclosure.
Internet邮件体系结构的核心不会对端到端或逐跳组件施加任何安全要求或功能。例如，它不需要参与者身份验证，也不试图阻止数据泄露。
Particular message attributes might expose specific security considerations. For example, the blind carbon copy feature of the architecture invites disclosure concerns, as discussed in Section 7.2 of [RFC5321] and Section 5 of [RFC5322]. Transport of text or non-text content in this architecture has security considerations that are discussed in [RFC5322], [RFC2045], [RFC2046], and [RFC4288]; also, security considerations are present for some of the media types registered with IANA.
特定的消息属性可能会暴露特定的安全注意事项。例如，如[RFC5321]第7.2节和[RFC5322]第5节所述，该体系结构的盲拷贝功能引起了公开关注。此体系结构中文本或非文本内容的传输具有[RFC5322]、[RFC2045]、[RFC2046]和[RFC4288]中讨论的安全注意事项；此外，在IANA注册的某些媒体类型也存在安全考虑。
Agents that automatically respond to email raise significant security considerations, as discussed in [RFC3834]. Gateway behaviors affect end-to-end security services, as discussed in [RFC2480]. Security considerations for boundary filters are discussed in [RFC5228].
如[RFC3834]中所述，自动响应电子邮件的代理会引起重要的安全注意事项。网关行为会影响端到端安全服务，如[RFC2480]中所述。[RFC5228]中讨论了边界过滤器的安全注意事项。
See Section 7.1 of [RFC5321] for a discussion of the topic of origination validation. As mentioned in Section 4.1.4, it is common practice for components of this architecture to use the RFC0791.SourceAddr to make policy decisions [RFC2505], although the address can be "spoofed". It is possible to use it without authorization. SMTP and Submission authentication ([RFC4409], [RFC4954]) provide more secure alternatives.
有关发起验证主题的讨论，请参见[RFC5321]第7.1节。如第4.1.4节所述，该体系结构的组件通常使用RFC0791.SourceAddr来做出策略决策[RFC2505]，尽管地址可能是“伪造的”。可以在未经授权的情况下使用它。SMTP和提交身份验证（[RFC4409]、[RFC4954]）提供了更安全的替代方案。
The discussion of trust boundaries, ADMDs, Actors, roles, and responsibilities in this document highlights the relevance and potential complexity of security factors for operation of an Internet Mail service. The core design of Internet Mail to encourage open and casual exchange of messages has met with scaling challenges, as the population of email participants has grown to include those with problematic practices. For example, spam, as defined in [RFC2505], is a by-product of this architecture. A number of Standards Track or BCP documents on the subject have been issued (see [RFC2505], [RFC5068], and [RFC5235]).
本文档中对信任边界、ADMD、参与者、角色和责任的讨论强调了Internet邮件服务运行的安全因素的相关性和潜在复杂性。互联网邮件的核心设计旨在鼓励公开和随意的邮件交流，但随着电子邮件参与者的数量增加，电子邮件参与者也越来越多，包括那些有问题的参与者，这一设计面临着扩展挑战。例如，[RFC2505]中定义的垃圾邮件就是这种体系结构的副产品。已经发布了许多关于该主题的标准跟踪或BCP文件（参见[RFC2505]、[RFC5068]和[RFC5235]）。
The core Internet email standards are based on the use of US-ASCII -- that is, SMTP [RFC5321] and IMF [RFC5322], as well as their predecessors. They describe the transport and composition of messages as composed strictly of US-ASCII 7-bit encoded characters. The standards have been incrementally enhanced to allow for characters outside of this limited set, while retaining mechanisms for backwards-compatibility. Specifically:
核心互联网电子邮件标准基于US-ASCII的使用——即SMTP[RFC5321]和IMF[RFC5322]，以及它们的前身。它们将消息的传输和组成描述为严格由US-ASCII 7位编码字符组成。这些标准已经得到了增量增强，以允许在这个有限集之外的字符，同时保留向后兼容的机制。明确地：
o The MIME specifications ([RFC2045], [RFC2046], [RFC2047], [RFC2049]) allow for the use of coded character sets and character-encoding schemes ("charsets" in MIME terminology) other than US-ASCII. MIME's [RFC2046] allows the textual content of a message to have a label affixed that specifies the charset used in that content. Equally, MIME's [RFC2047] allows the textual content of certain header fields in a message to be similarly labeled. However, since messages might be transported over SMTP implementations only capable of transporting 7-bit encoded characters, MIME's [RFC2045] also provides for "content transfer encoding" so that characters of other charsets can be re-encoded as an overlay to US-ASCII.
o MIME规范（[RFC2045]、[RFC2046]、[RFC2047]、[RFC2049]）允许使用US-ASCII以外的编码字符集和字符编码方案（“MIME术语中的字符集”）。MIME的[RFC2046]允许消息的文本内容粘贴一个标签，指定该内容中使用的字符集。同样，MIME的[RFC2047]允许对消息中某些头字段的文本内容进行类似的标记。然而，由于邮件可能通过SMTP实现传输，只能传输7位编码字符，MIME的[RFC2045]还提供了“内容传输编码”，因此其他字符集的字符可以作为US-ASCII的覆盖重新编码。
o MIME's [RFC2045] allows for the textual content of a message to be in an 8-bit character-encoding scheme. In order to transport these without re-encoding them, the SMTP specification supports an option [RFC1652] that permits the transport of such textual
o MIME的[RFC2045]允许消息的文本内容采用8位字符编码方案。为了在不重新编码的情况下传输这些内容，SMTP规范支持允许传输此类文本内容的选项[RFC1652]
content. However, the [RFC1652] option does not address the use of 8-bit content in message header fields, and therefore [RFC2047] encoding is still required for those.
所容纳之物但是，[RFC1652]选项不能解决消息头字段中8位内容的使用问题，因此这些字段仍然需要[RFC2047]编码。
o A series of experimental protocols on Email Address Internationalization (EAI) have been released that extend SMTP and IMF to allow for 8-bit encoded characters to appear in addresses and other information throughout the header fields of messages. [RFC5335] specifies the format of such message header fields (which encode the characters in UTF-8), and [RFC5336] specifies an SMTP option for the transport of these messages.
o 一系列关于电子邮件地址国际化（EAI）的实验协议已经发布，这些协议扩展了SMTP和IMF，允许8位编码字符出现在地址和消息头字段中的其他信息中。[RFC5335]指定此类邮件标题字段的格式（对UTF-8中的字符进行编码），[RFC5336]指定用于传输这些邮件的SMTP选项。
o MIME's [RFC2045] and [RFC2046] allow for the transport of true multimedia material; such material enables internationalization because it is not restricted to any particular language or locale.
o MIME的[RFC2045]和[RFC2046]允许传输真实的多媒体材料；这种材料支持国际化，因为它不限于任何特定的语言或地区。
o The formats for Delivery Status Notifications (DSNs -- [RFC3462], [RFC3463], [RFC3464]) and Message Disposition Notifications (MDNs -- [RFC3798]) include both a structured and unstructured representation of the notification. In the event that the unstructured representation is in the wrong language or is otherwise unsuitable for use, this allows an MUA to construct its own appropriately localized representation of notification for display to the User.
o 传递状态通知（DSN--[RFC3462]、[RFC3463]、[RFC3464]）和消息处置通知（MDN--[RFC3798]）的格式包括通知的结构化和非结构化表示。如果非结构化表示使用了错误的语言或不适合使用，这允许MUA构建自己的通知的适当本地化表示，以显示给用户。
o POP and IMAP have no difficulties with handling MIME messages, including ones containing 8bit, and therefore are not a source of internationalization issues.
o POP和IMAP在处理MIME消息（包括包含8位的消息）方面没有困难，因此不是国际化问题的根源。
Hence, the use of UTF-8 is fully established in existing Internet Mail. However, support for long-standing encoding forms is retained and is still used.
因此，UTF-8的使用在现有的互联网邮件中已完全确立。但是，对长期存在的编码形式的支持被保留并仍在使用。
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981.
[RFC0791]Postel，J.，“互联网协议”，STD 5，RFC 7911981年9月。
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987.
[RFC1034]Mockapetris，P.，“域名-概念和设施”，STD 13，RFC 1034，1987年11月。
[RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987.
[RFC1035]Mockapetris，P.，“域名-实现和规范”，STD 13，RFC 1035，1987年11月。
[RFC1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3", STD 53, RFC 1939, May 1996.
[RFC1939]迈尔斯，J.和M.罗斯，“邮局协议-第3版”，STD 53，RFC 1939，1996年5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。
[RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples", RFC 2049, November 1996.
[RFC2049]Freed，N.和N.Borenstein，“多用途Internet邮件扩展（MIME）第五部分：一致性标准和示例”，RFC 2049，1996年11月。
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS Specification", RFC 2181, July 1997.
[RFC2181]Elz，R.和R.Bush，“DNS规范的澄清”，RFC 21811997年7月。
[RFC2369] Neufeld, G. and J. Baer, "The Use of URLs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields", RFC 2369, July 1998.
[RFC2369]Neufeld，G.和J.Baer，“使用URL作为核心邮件列表命令的元语法及其通过消息头字段的传输”，RFC 2369，1998年7月。
[RFC2645] Gellens, R., "ON-DEMAND MAIL RELAY (ODMR) SMTP with Dynamic IP Addresses", RFC 2645, August 1999.
[RFC2645]Gellens，R.，“具有动态IP地址的按需邮件中继（ODMR）SMTP”，RFC 26451999年8月。
[RFC2919] Chandhok, R. and G. Wenger, "List-Id: A Structured Field and Namespace for the Identification of Mailing Lists", RFC 2919, March 2001.
[RFC2919]Chandhok，R.和G.Wenger，“列表Id：用于识别邮件列表的结构化字段和名称空间”，RFC 2919，2001年3月。
[RFC3192] Allocchio, C., "Minimal FAX address format in Internet Mail", RFC 3192, October 2001.
[RFC3192]Allocchio，C.，“互联网邮件中的最小传真地址格式”，RFC3192，2001年10月。
[RFC3297] Klyne, G., Iwazaki, R., and D. Crocker, "Content Negotiation for Messaging Services based on Email", RFC 3297, July 2002.
[RFC3297]Klyne，G.，Iwazaki，R.，和D.Crocker，“基于电子邮件的消息传递服务的内容协商”，RFC 3297，2002年7月。
[RFC3458] Burger, E., Candell, E., Eliot, C., and G. Klyne, "Message Context for Internet Mail", RFC 3458, January 2003.
[RFC3458]Burger，E.，Candell，E.，Eliot，C.，和G.Klyne，“互联网邮件的消息上下文”，RFC 3458，2003年1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。
[RFC3462] Vaudreuil, G., "The Multipart/Report Content Type for the Reporting of Mail System Administrative Messages", RFC 3462, January 2003.
[RFC3462]Vaudreuil，G.“用于报告邮件系统管理消息的多部分/报告内容类型”，RFC 3462，2003年1月。
[RFC3463] Vaudreuil, G., "Enhanced Mail System Status Codes", RFC 3463, January 2003.
[RFC3463]Vaudreuil，G.，“增强邮件系统状态代码”，RFC 3463，2003年1月。
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1", RFC 3501, March 2003.
[RFC3501]Crispin，M.，“互联网消息访问协议-版本4rev1”，RFC 35012003年3月。
[RFC3798] Hansen, T. and G. Vaudreuil, "Message Disposition Notification", RFC 3798, May 2004.
[RFC3798]Hansen，T.和G.Vaudreuil，“消息处置通知”，RFC 3798，2004年5月。
[RFC3834] Moore, K., "Recommendations for Automatic Responses to Electronic Mail", RFC 3834, August 2004.
[RFC3834]Moore，K.，“自动回复电子邮件的建议”，RFC 38342004年8月。
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004.
[RFC3864]Klyne，G.，Nottingham，M.和J.Mogul，“消息头字段的注册程序”，BCP 90，RFC 3864，2004年9月。
[RFC4021] Klyne, G. and J. Palme, "Registration of Mail and MIME Header Fields", RFC 4021, March 2005.
[RFC4021]Klyne，G.和J.Palme，“邮件和MIME头字段的注册”，RFC4021，2005年3月。
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and Registration Procedures", BCP 13, RFC 4288, December 2005.
[RFC4288]Freed，N.和J.Klensin，“介质类型规范和注册程序”，BCP 13，RFC 4288，2005年12月。
[RFC4289] Freed, N. and J. Klensin, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 4289, December 2005.
[RFC4289]Freed，N.和J.Klensin，“多用途互联网邮件扩展（MIME）第四部分：注册程序”，BCP 13，RFC 4289，2005年12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。
[RFC4550] Maes, S. and A. Melnikov, "Internet Email to Support Diverse Service Environments (Lemonade) Profile", RFC 4550, June 2006.
[RFC4550]Maes，S.和A.Melnikov，“支持多样化服务环境的互联网电子邮件（柠檬水）简介”，RFC 45502006年6月。
[RFC5228] Guenther, P. and T. Showalter, "Sieve: An Email Filtering Language", RFC 5228, January 2008.
[RFC5228]Guenther，P.和T.Showalter，“筛选：电子邮件过滤语言”，RFC 5228，2008年1月。
[RFC5248] Hansen, T. and J. Klensin, "A Registry for SMTP Enhanced Mail System Status Codes", BCP 138, RFC 5248, June 2008.
[RFC5248]Hansen，T.和J.Klensin，“SMTP增强邮件系统状态代码的注册表”，BCP 138，RFC 5248，2008年6月。
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, October 2008.
[RFC5321]Klensin，J.，“简单邮件传输协议”，RFC 53212008年10月。
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, October 2008.
[RFC5322]Resnick，P.，Ed.“互联网信息格式”，RFC5222008年10月。
[RFC0733] Crocker, D., Vittal, J., Pogran, K., and D. Henderson, "Standard for the format of ARPA network text messages", RFC 733, November 1977.
[RFC0733]Crocker，D.，Vittal，J.，Pogran，K.，和D.Henderson，“ARPA网络文本消息格式标准”，RFC 733，1977年11月。
[RFC0821] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, August 1982.
[RFC0821]Postel，J.，“简单邮件传输协议”，STD 10，RFC 821，1982年8月。
[RFC0822] Crocker, D., "Standard for the format of ARPA Internet text messages", STD 11, RFC 822, August 1982.
[RFC0822]Crocker，D.，“ARPA互联网文本信息格式标准”，STD 11，RFC 822，1982年8月。
[RFC1506] Houttuin, J., "A Tutorial on Gatewaying between X.400 and Internet Mail", RFC 1506, August 1993.
[RFC1506]Houttuin，J.，“X.400和互联网邮件之间的网关教程”，RFC1506，1993年8月。
[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。
[RFC1733] Crispin, M., "Distributed Electronic Mail Models in IMAP4", RFC 1733, December 1994.
[RFC1733]Crispin，M.，“IMAP4中的分布式电子邮件模型”，RFC 1733，1994年12月。
[RFC1767] Crocker, D., "MIME Encapsulation of EDI Objects", RFC 1767, March 1995.
[RFC1767]Crocker，D.，“EDI对象的MIME封装”，RFC17671995年3月。
[RFC1985] De Winter, J., "SMTP Service Extension for Remote Message Queue Starting", RFC 1985, August 1996.
[RFC1985]De Winter，J.，“远程消息队列启动的SMTP服务扩展”，RFC 1985，1996年8月。
[RFC2033] Myers, J., "Local Mail Transfer Protocol", RFC 2033, October 1996.
[RFC2033]迈尔斯，J.，“本地邮件传输协议”，RFC20331996年10月。
[RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND FUNCTIONS", RFC 2142, May 1997.
[RFC2142]Crocker，D.，“公共服务、角色和功能的邮箱名称”，RFC 2142，1997年5月。
[RFC2442] Freed, N., Newman, D., and Hoy, M., "The Batch SMTP Media Type", RFC 2442, November 1998.
[RFC2442]弗里德，N.，纽曼，D.，和霍伊，M.，“批量SMTP媒体类型”，RFC 24421998年11月。
[RFC2480] Freed, N., "Gateways and MIME Security Multiparts", RFC 2480, January 1999.
[RFC2480]弗里德，N.，“网关和MIME安全多部分”，RFC2480，1999年1月。
[RFC2505] Lindberg, G., "Anti-Spam Recommendations for SMTP MTAs", BCP 30, RFC 2505, February 1999.
[RFC2505]Lindberg，G.，“SMTP MTA的反垃圾邮件建议”，BCP 30，RFC 2505，1999年2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。
[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。
[RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over Transport Layer Security", RFC 3207, February 2002.
[RFC3207]Hoffman，P.，“传输层安全SMTP的SMTP服务扩展”，RFC3207，2002年2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。
[RFC3801] Vaudreuil, G. and G. Parsons, "Voice Profile for Internet Mail - version 2 (VPIMv2)", RFC 3801, June 2004.
[RFC3801]Vaudreuil，G.和G.Parsons，“互联网邮件语音配置文件-第2版（VPIMv2）”，RFC 38012004年6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。
[RFC3885] Allman, E. and T. Hansen, "SMTP Service Extension for Message Tracking", RFC 3885, September 2004.
[RFC3885]Allman，E.和T.Hansen，“用于邮件跟踪的SMTP服务扩展”，RFC 38852004年9月。
[RFC4142] Crocker, D. and G. Klyne, "Full-mode Fax Profile for Internet Mail (FFPIM)", RFC 4142, November 2005.
[RFC4142]Crocker，D.和G.Klyne，“互联网邮件的全模式传真配置文件（FFPIM）”，RFC 41422005年11月。
[RFC4143] Toyoda, K. and D. Crocker, "Facsimile Using Internet Mail (IFAX) Service of ENUM", RFC 4143, November 2005.
[RFC4143]丰田章男，K.和D.克罗克，“使用ENUM的互联网邮件（IFAX）服务进行传真”，RFC 41432005年11月。
[RFC4356] Gellens, R., "Mapping Between the Multimedia Messaging Service (MMS) and Internet Mail", RFC 4356, January 2006.
[RFC4356]Gellens，R.，“多媒体信息服务（MMS）和互联网邮件之间的映射”，RFC 4356，2006年1月。
[RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R. Thayer, "OpenPGP Message Format", RFC 4880, November 2007.
[RFC4880]Callas，J.，Donnerhacke，L.，Finney，H.，Shaw，D.，和R.Thayer，“OpenPGP消息格式”，RFC 48802007年11月。
[RFC4954] Siemborski, R. and A. Melnikov, "SMTP Service Extension for Authentication", RFC 4954, July 2007.
[RFC4954]Siemborski，R.和A.Melnikov，“用于身份验证的SMTP服务扩展”，RFC 49542007年7月。
[RFC5068] Hutzler, C., Crocker, D., Resnick, P., Allman, E., and T. Finch, "Email Submission Operations: Access and Accountability Requirements", BCP 134, RFC 5068, November 2007.
[RFC5068]Hutzler，C.，Crocker，D.，Resnick，P.，Allman，E.，和T.Finch，“电子邮件提交操作：访问和责任要求”，BCP 134，RFC 5068，2007年11月。
[RFC5235] Daboo, C., "Sieve Email Filtering: Spamtest and Virustest Extensions", RFC 5235, January 2008.
[RFC5235]Daboo，C.，“筛选电子邮件过滤：垃圾邮件测试和病毒测试扩展”，RFC5352008年1月。
[RFC5335] Abel, Y., "Internationalized Email Headers", RFC 5335, September 2008.
[RFC5335]Abel，Y.，“国际化电子邮件标题”，RFC 53352008年9月。
[RFC5336] Yao, J. and W. Mao, "SMTP Extension for Internationalized Email Addresses", RFC 5336, September 2008.
[RFC5336]Yao，J.和W.Mao，“国际化电子邮件地址的SMTP扩展”，RFC 53362008年9月。
[Tussle] Clark, D., Wroclawski, J., Sollins, K., and R. Braden, "Tussle in Cyberspace: Defining Tomorrow's Internet", ACM SIGCOMM, 2002.
[Tussle]Clark，D.，Wroclawski，J.，Sollins，K.，和R.Braden，“网络空间中的争斗：定义明天的互联网”，ACM SIGCOMM，2002年。
This work began in 2004 and has evolved through numerous rounds of community review; it derives from a section in an early version of [RFC5068]. Over its 5 years of development, the document has gone through 14 incremental versions, with vigorous community review that produced many substantive changes. Review was performed in the IETF and other email technical venues. Although not a formal activity of the IETF, issues with the document's contents were resolved using the classic style of IETF community open, group decision-making. The document is already cited in other work, such as in IMAP and Sieve specifications and in academic classwork. The step of standardizing is useful to provide a solid and stable reference to the Internet's now-complex email service.
这项工作始于2004年，并通过多轮社区审查进行了演变；它源自[RFC5068]早期版本中的一节。在其5年的发展过程中，该文件经历了14个增量式版本，并进行了积极的社区审查，产生了许多实质性变化。审查在IETF和其他电子邮件技术场所进行。虽然不是IETF的正式活动，但文件内容的问题是使用IETF社区开放式群体决策的经典风格解决的。该文件已在其他工作中引用，如IMAP和筛规范以及学术课堂工作中。标准化的步骤有助于为互联网现在复杂的电子邮件服务提供可靠和稳定的参考。
Details of the Originator Actor role was greatly clarified during discussions in the IETF's Marid working group.
在IETF的Marid工作组的讨论中，发起人-参与者角色的细节得到了极大的澄清。
Graham Klyne, Pete Resnick, and Steve Atkins provided thoughtful insight on the framework and details of the original drafts, as did Chris Newman for the final versions, while also serving as cognizant Area Director for the document. Tony Hansen served as document shepherd through the IETF process.
格雷厄姆·克莱恩（Graham Klyne）、皮特·雷斯尼克（Pete Resnick）和史蒂夫·阿特金斯（Steve Atkins）为原始草案的框架和细节提供了深思熟虑的见解，克里斯·纽曼（Chris Newman）也为最终版本提供了见解，同时还担任了该文件的认可区域主管。Tony Hansen在IETF过程中担任文档管理员。
Later reviews and suggestions were provided by Eric Allman, Nathaniel Borenstein, Ed Bradford, Cyrus Daboo, Frank Ellermann, Tony Finch, Ned Freed, Eric Hall, Willemien Hoogendoorn, Brad Knowles, John Leslie, Bruce Valdis Kletnieks, Mark E. Mallett, David MacQuigg, Alexey Melnikov, der Mouse, S. Moonesamy, Daryl Odnert, Rahmat M. Samik-Ibrahim, Marshall Rose, Hector Santos, Jochen Topf, Greg Vaudreuil, Patrick Cain, Paul Hoffman, Vijay Gurbani, and Hans Lachman.
后来，埃里克·奥尔曼、纳撒尼尔·博伦斯坦、埃德·布拉德福德、塞勒斯·达布、弗兰克·埃勒曼、托尼·芬奇、内德·弗里德、埃里克·霍尔、威廉·胡根杜恩、布拉德·诺尔斯、约翰·莱斯利、布鲁斯·瓦尔迪斯·克莱特涅克斯、马克·马莱特、大卫·麦奎格、阿列克谢·梅尔尼科夫、德·穆内斯米、达里尔·奥德纳特、拉马特·萨米克·易卜拉欣、，马歇尔·罗斯、赫克托·桑托斯、约亨·托普夫、格雷格·沃德鲁伊、帕特里克·凯恩、保罗·霍夫曼、维杰·古巴尼和汉斯·拉克曼。
Diligent early proof-reading was performed by Bruce Lilly. Diligent professional technical editing was provided by Susan Hunziker.
布鲁斯·莉莉（Bruce Lilly）进行了勤奋的早期校对。Susan Hunziker提供了勤奋的专业技术编辑。
The final stages of development for this document were guided by a design team comprising Alexey Melnikov, Pete Resnick, Carl S. Gutekunst, Jeff Macdonald, Randall Gellens, Tony Hansen, and Tony Finch. Pete Resnick developed the final version of the section on internationalization.
本文件的最终开发阶段由一个设计团队指导，该团队由Alexey Melnikov、Pete Resnick、Carl S.Gutekunst、Jeff Macdonald、Randall Gellens、Tony Hansen和Tony Finch组成。Pete Resnick开发了国际化部分的最终版本。
Index
指数
7 7-bit 44
7位44
A accountability 12 accountable 13-14 Actor Administrative 14 Author 10 Consumer 15 Edge 15 Gateway 13 Originator 12 Recipient 10 Return Handler 10 Transit 15 actor 7, 19, 26, 28-29, 35-36, 38-40, 42-43, 49 Actors MHS 11 addr-spec 17 address addr-spec 17 local-part 18 ADMD 12, 14-15, 19, 25, 31, 37 Administrative Actors 14 Administrative Management Domain 12 aMSA 31 Author 10-11 author 35
责任12责任13-14参与者管理14作者10消费者15边缘15网关13发起人12接收人10退货处理人10中转15参与者7、19、26、28-29、35-36、38-40、42-43、49参与者MHS 11地址规范17地址地址规范17本地部分18 ADMD 12、14-15、19、25、31、，37行政参与者14行政管理领域12 aMSA 31作者10-11作者35
B body parts 24 bounce handler 10 boundary 15
B车身部件24弹跳处理器10边界15
C charset 44 Consumer Actor 15 content 11, 13-14, 20, 24, 32
C字符集44消费者演员15内容11、13-14、20、24、32
D delivery 4, 10-11, 13-14, 18, 24-25, 35, 37-38 Discussion of document 7 domain name 17, 21, 28 DSN 44
D交付4、10-11、13-14、18、24-25、35、37-38讨论文件7域名17、21、28 DSN 44
E EAI 44 Edge Actor 15 encoding 44 end-to-end 4-6, 11, 15, 28
EAI 44边缘参与者15编码44端到端4-6、11、15、28
envelope 10, 13, 21, 24-25, 32, 37 ETRN 35
信封10、13、21、24-25、32、37 ETRN 35
G Gateway 11, 13 gateway 6, 12-13, 18, 25, 32
G网关11、13网关6、12-13、18、25、32
H header 24 hMSA 31
H收割台24 hMSA 31
I identifier 18-19, 21, 25, 29 IMAP 24, 31, 34-35, 44 IMF 19, 24, 44 Internet Mail 4
I标识符18-19、21、25、29 IMAP 24、31、34-35、44 IMF 19、24、44 Internet Mail 4
L left-hand side 18 LMTP 24, 35 local-part 18
L左侧18 LMTP 24，35局部18
M Mail 4 Mail From 37 Mail Submission Agent 12 mailbox 17, 19, 24, 28, 30, 33, 37-38 MDA 24, 37 MDN 10, 24, 44 message 6, 24 Message Disposition Notification 10 Message Handling Service 4 Message Handling System 11 Message Transfer Agent 4 Message User Agent 4 MHS 4, 10-13, 21-22, 24-25 Actors 11 MIME 24, 44 MS 24 MSA 12, 24, 31 MTA 4, 15 boundary 15
M Mail 4来自37邮件提交代理12邮箱17、19、24、28、30、33、37-38 MDA 24、37 MDN 10、24、44消息6、24消息处置通知10消息处理服务4消息处理系统11消息传输代理4消息用户代理4 MHS 4、10-13、21-22、24-25参与者11 MIME 24、44 MS 24 MSA 12、24、31 MTA 4，15边界15
MUA 4, 14, 24, 30-31
MUA 4、14、24、30-31
O ODMR 35 operations 3, 15, 18, 29, 40 Originator 10-12
O ODMR 35运营3、15、18、29、40发起人10-12
P POP 24, 31, 34-35, 44 posting 4, 10, 12, 21, 30-31, 35, 37 pull 35 push 35
P POP 24,31,34-35,44张贴4,10,12,21,30-31,35,37拉35推35
R RcptTo 11 Receiver 11 Recipient 10-11, 37 recipient 35 relay 11 responsibility 31 responsible 13-14 Return Address 37 Return Handler 10 role 10, 18 Author 10 Originator 12 Recipient 10
R RcptTo 11接收者11接收者10-11，37接收者35中继11责任31责任13-14返回地址37返回处理者10角色10，18作者10发起人12接收者10
S SIEVE 24-25 SMTP 24, 35, 44
S筛24-25 SMTP 24、35、44
T transfer 11, 13-14 Transit Actor 15 transition 31
T转换11、13-14转换执行器15转换31
U UA 4 User Agent 4
U UA 4用户代理4
Author's Address
作者地址
Dave Crocker Brandenburg InternetWorking 675 Spruce Drive Sunnyvale, CA 94086 USA
戴夫·克罗克·勃兰登堡互联网络美国加利福尼亚州桑尼维尔市云杉大道675号，邮编94086
Phone: +1.408.246.8253
EMail: dcrocker@bbiw.net
Phone: +1.408.246.8253
EMail: dcrocker@bbiw.net