Internet Engineering Task Force (IETF) R. Gellens
Request for Comments: 6856 QUALCOMM Incorporated
Obsoletes: 5721 C. Newman
Category: Standards Track Oracle
ISSN: 2070-1721 J. Yao
CNNIC
K. Fujiwara
JPRS
March 2013
Internet Engineering Task Force (IETF) R. Gellens
Request for Comments: 6856 QUALCOMM Incorporated
Obsoletes: 5721 C. Newman
Category: Standards Track Oracle
ISSN: 2070-1721 J. Yao
CNNIC
K. Fujiwara
JPRS
March 2013
Post Office Protocol Version 3 (POP3) Support for UTF-8
邮局协议版本3（POP3）支持UTF-8
Abstract
摘要
This specification extends the Post Office Protocol version 3 (POP3) to support international strings encoded in UTF-8 in usernames, passwords, mail addresses, message headers, and protocol-level text strings.
本规范扩展了邮局协议版本3（POP3），以支持用户名、密码、邮件地址、消息头和协议级文本字符串中以UTF-8编码的国际字符串。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6856.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc6856.
Copyright Notice
版权公告
Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2013 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。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。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
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 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.
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，也不得在IETF标准流程之外创建其衍生作品，除了将其格式化以RFC形式发布或将其翻译成英语以外的其他语言。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. "UTF8" Capability . . . . . . . . . . . . . . . . . . . . . . 4
2.1. The "UTF8" Command . . . . . . . . . . . . . . . . . . . . 5
2.2. USER Argument to "UTF8" Capability . . . . . . . . . . . . 6
3. "LANG" Capability . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Non-ASCII Character Maildrops . . . . . . . . . . . . . . . . 9
5. "UTF8" Response Code . . . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Appendix A. Design Rationale . . . . . . . . . . . . . . . . . . 13
Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . . 13
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. "UTF8" Capability . . . . . . . . . . . . . . . . . . . . . . 4
2.1. The "UTF8" Command . . . . . . . . . . . . . . . . . . . . 5
2.2. USER Argument to "UTF8" Capability . . . . . . . . . . . . 6
3. "LANG" Capability . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Non-ASCII Character Maildrops . . . . . . . . . . . . . . . . 9
5. "UTF8" Response Code . . . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Appendix A. Design Rationale . . . . . . . . . . . . . . . . . . 13
Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . . 13
This document forms part of the Email Address Internationalization protocols described in the Email Address Internationalization Framework document [RFC6530]. As part of the overall Email Address Internationalization work, email messages can be transmitted and delivered containing a Unicode string encoded in UTF-8 in the header and/or body, and maildrops that are accessed using POP3 [RFC1939] might natively store Unicode characters.
本文档构成电子邮件地址国际化框架文档[RFC6530]中描述的电子邮件地址国际化协议的一部分。作为整个电子邮件地址国际化工作的一部分，可以传输和传递电子邮件消息，邮件头和/或正文中包含以UTF-8编码的Unicode字符串，使用POP3[RFC1939]访问的邮件投递可能本机存储Unicode字符。
This specification extends POP3 using the POP3 extension mechanism [RFC2449] to permit un-encoded UTF-8 [RFC3629] in headers and bodies (e.g., transferred using 8-bit content-transfer-encoding) as described in "Internationalized Email Headers" [RFC6532]. It also adds a mechanism to support login names and passwords containing a UTF-8 string (see Section 1.1 below), a mechanism to support UTF-8 strings in protocol-level response strings, and the ability to negotiate a language for such response strings.
本规范使用POP3扩展机制[RFC2449]扩展POP3，以允许在标题和正文中使用未编码的UTF-8[RFC3629]（例如，使用8位内容传输编码传输），如“国际化电子邮件标题”[RFC6532]中所述。它还添加了一种机制来支持包含UTF-8字符串的登录名和密码（请参见下面的第1.1节），一种机制来支持协议级响应字符串中的UTF-8字符串，以及为此类响应字符串协商语言的能力。
This specification also adds a new response code to indicate that a message was not delivered because it required UTF-8 mode (as discussed in Section 2) and the server was unable or unwilling to create and deliver a surrogate form of the message as discussed in Section 7 of "IMAP Support for UTF-8" [RFC6855].
本规范还添加了一个新的响应代码，以指示未传递消息，因为它需要UTF-8模式（如第2节所述），并且服务器无法或不愿意创建和传递“对UTF-8的IMAP支持”[RFC6855]第7节所述的消息的替代形式。
This specification replaces an earlier, experimental, approach to the same problem [RFC5721].
本规范取代了以前针对同一问题的实验性方法[RFC5721]。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照“RFC中用于指示需求水平的关键词”[RFC2119]中的描述进行解释。
The terms "UTF-8 string" or "UTF-8 character" are used to refer to Unicode characters, which may or may not be members of the ASCII repertoire, encoded in UTF-8 [RFC3629], a standard Unicode encoding form. All other specialized terms used in this specification are defined in the Email Address Internationalization framework document.
术语“UTF-8字符串”或“UTF-8字符”用于指Unicode字符，这些字符可能是也可能不是ASCII指令集的成员，以标准Unicode编码形式UTF-8[RFC3629]编码。本规范中使用的所有其他专用术语在电子邮件地址国际化框架文档中定义。
In examples, "C:" and "S:" indicate lines sent by the client and server, respectively. If a single "C:" or "S:" label applies to multiple lines, then the line breaks between those lines are for editorial clarity only and are not part of the actual protocol exchange.
在示例中，“C:”和“S:”分别表示客户端和服务器发送的行。如果单个“C:”或“S:”标签适用于多行，则这些行之间的换行符仅用于编辑清晰性，不属于实际协议交换的一部分。
Note that examples always use ASCII characters due to limitations of the RFC format; otherwise, some examples for the "LANG" command would have appeared incorrectly.
注意，由于RFC格式的限制，示例始终使用ASCII字符；否则，“LANG”命令的一些示例可能会出现错误。
This specification adds a new POP3 Extension [RFC2449] capability response tag and command to specify support for header field information outside the ASCII repertoire. The capability tag and new command and functionality are described below.
本规范添加了一个新的POP3扩展[RFC2449]功能响应标记和命令，以指定对ASCII指令表之外的标题字段信息的支持。下面描述了功能标签以及新的命令和功能。
CAPA tag: UTF8
CAPA标签：UTF8
Arguments with CAPA tag: USER
带有CAPA标记的参数：USER
Added Commands: UTF8
添加命令：UTF8
Standard commands affected: USER, PASS, APOP, LIST, TOP, RETR
受影响的标准命令：USER、PASS、APOP、LIST、TOP、RETR
Announced states / possible differences: both / no
宣布的州/可能的差异：两者/否
Commands valid in states: AUTHORIZATION
在以下状态下有效的命令：授权
Specification reference: this document
规范参考：本文件
Discussion:
讨论：
This capability adds the "UTF8" command to POP3. The "UTF8" command switches the session from the ASCII-only mode of POP3 [RFC1939] to UTF-8 mode. The UTF-8 mode means that all messages transmitted between servers and clients are UTF-8 strings, and both servers and clients can send and accept UTF-8 strings.
此功能将“UTF8”命令添加到POP3中。“UTF8”命令将会话从POP3[RFC1939]的仅ASCII模式切换到UTF-8模式。UTF-8模式意味着服务器和客户端之间传输的所有消息都是UTF-8字符串，服务器和客户端都可以发送和接受UTF-8字符串。
The "UTF8" command enables UTF-8 mode. The "UTF8" command has no parameters.
“UTF8”命令启用UTF-8模式。“UTF8”命令没有参数。
UTF-8 mode has no effect on messages in an ASCII-only maildrop. Messages in native Unicode maildrops can be encoded in UTF-8 using internationalized headers [RFC6532], in 8bit content-transfer-encoding (see Section 2.8 of MIME [RFC2045]), in ASCII, or in any combination of these options. In UTF-8 mode, if the character encoding format of maildrops is UTF-8 or ASCII, the messages are sent to the client as is; if the character encoding format of maildrops is a format other than UTF-8 or ASCII, the messages' encoding format SHOULD be converted to be UTF-8 before they are sent to the client. When UTF-8 mode has not been enabled, character strings outside the ASCII repertoire MUST NOT be sent to the client as is. If a client requests a UTF-8 message when UTF-8 mode is not enabled, the server MUST either send the client a surrogate message that complies with unextended POP and Internet Mail Format without UTF-8 mode support, or fail the request with an -ERR response. See Section 7 of "IMAP Support for UTF-8" [RFC6855] for information about creating a surrogate message and for a discussion of potential issues. Section 5 of this document discusses "UTF8" response codes. The server MAY respond to the "UTF8" command with an -ERR response.
UTF-8模式对仅ASCII邮件投递中的邮件没有影响。本机Unicode邮件投递中的消息可以使用国际化头[RFC6532]、8位内容传输编码（请参阅MIME[RFC2045]第2.8节）、ASCII或这些选项的任意组合以UTF-8进行编码。在UTF-8模式下，如果Maildrop的字符编码格式为UTF-8或ASCII，则消息按原样发送到客户端；如果Maildrop的字符编码格式不是UTF-8或ASCII格式，则消息的编码格式应在发送到客户端之前转换为UTF-8。未启用UTF-8模式时，ASCII指令表之外的字符串不得按原样发送到客户端。如果客户端在未启用UTF-8模式时请求UTF-8消息，则服务器必须向客户端发送符合未扩展的POP和Internet邮件格式且不支持UTF-8模式的代理消息，或者通过-ERR响应使请求失败。有关创建代理消息的信息和潜在问题的讨论，请参见“UTF-8的IMAP支持”[RFC6855]的第7节。本文件第5节讨论了“UTF8”响应代码。服务器可能会以-ERR响应“UTF8”命令。
Note that even in UTF-8 mode, MIME binary content-transfer-encoding as defined in Section 6.2 of MIME [RFC2045] is still not permitted. MIME 8bit content-transfer-encoding (8BITMIME) [RFC6152] is obviously allowed.
请注意，即使在UTF-8模式下，MIME[RFC2045]第6.2节中定义的MIME二进制内容传输编码仍然是不允许的。MIME 8bit内容传输编码（8bit MIME）[RFC6152]显然是允许的。
The octet count (size) of a message reported in a response to the "LIST" command SHOULD match the actual number of octets sent in a "RETR" response (not counting byte-stuffing). Sizes reported elsewhere, such as in "STAT" responses and non-standardized, free-form text in positive status indicators (following "+OK") need not be accurate, but it is preferable if they are.
在对“LIST”命令的响应中报告的消息的八位字节计数（大小）应与在“RETR”响应中发送的八位字节的实际数量相匹配（不计算字节填充）。其他地方报告的大小，如“统计”响应中的大小和积极状态指示器中的非标准、自由格式文本（在“+OK”之后）不需要准确，但如果准确则更好。
Normal operation for maildrops that natively support non-ASCII characters will be for both servers and clients to support the extension discussed in this specification. Upgrading both clients and servers is the only fully satisfactory way to support the capabilities offered by the "UTF8" extension and SMTPUTF8 mail more generally. Servers must, however, anticipate the possibility of a client attempting to access a message that requires this extension without having issued the "UTF8" command. There are no completely satisfactory responses for this case other than upgrading the client to support this specification. One solution, unsatisfactory because
本机支持非ASCII字符的邮件投递的正常操作将用于服务器和客户端，以支持本规范中讨论的扩展。升级客户端和服务器是支持“UTF8”扩展和SMTPUTF8邮件提供的功能的唯一完全令人满意的方法。但是，服务器必须预测客户端在未发出“UTF8”命令的情况下尝试访问需要此扩展的消息的可能性。对于这种情况，除了升级客户端以支持此规范之外，没有完全令人满意的响应。一个解决方案不令人满意，因为
the user may be confused by being able to access the message through some means and not others, is that a server MAY choose to reject the command to retrieve the message as discussed in Section 5. Other alternatives, including the possibility of creating and delivering a surrogate form of the message, are discussed in Section 7 of "IMAP Support for UTF-8" [RFC6855].
用户可能会因为能够通过某些方式而不是其他方式访问消息而感到困惑，因为服务器可能会选择拒绝检索消息的命令，如第5节所述。“UTF-8的IMAP支持”[RFC6855]第7节讨论了其他备选方案，包括创建和交付消息代理形式的可能性。
Clients MUST NOT issue the "STLS" command [RFC2595] after issuing UTF8; servers MAY (but are not required to) enforce this by rejecting with an -ERR response an "STLS" command issued subsequent to a successful "UTF8" command. (Because this is a protocol error as opposed to a failure based on conditions, an extended response code [RFC2449] is not specified.)
客户端在发出UTF8后不得发出“STLS”命令[RFC2595]；服务器可以（但不需要）通过使用-ERR响应拒绝在成功的“UTF8”命令之后发出的“STLS”命令来强制执行此操作。（由于这是协议错误，而不是基于条件的故障，因此未指定扩展响应代码[RFC2449]）
If the USER argument is included with this capability, it indicates that the server accepts UTF-8 usernames and passwords.
如果此功能包含用户参数，则表示服务器接受UTF-8用户名和密码。
Servers that include the USER argument in the "UTF8" capability response SHOULD apply SASLprep [RFC4013] or one of its Standards Track successors to the arguments of the "USER" and "PASS" commands.
在“UTF8”功能响应中包含用户参数的服务器应应用SASLprep[RFC4013]或其标准跟踪“USER”和“PASS”命令参数的后续。
A client or server that supports APOP and permits UTF-8 in usernames or passwords MUST apply SASLprep or one of its Standards Track successors to the username and password used to compute the APOP digest.
支持APOP并在用户名或密码中允许UTF-8的客户端或服务器必须将SASLprep或其标准跟踪继承者之一应用于用于计算APOP摘要的用户名和密码。
When applying SASLprep, servers MUST reject UTF-8 usernames or passwords that contain a UTF-8 character listed in Section 2.3 of SASLprep. When applying SASLprep to the USER argument, the PASS argument, or the APOP username argument, a compliant server or client MUST treat them as a query string [RFC3454]. When applying SASLprep to the APOP password argument, a compliant server or client MUST treat them as a stored string [RFC3454].
应用SASLprep时，服务器必须拒绝包含SASLprep第2.3节中列出的UTF-8字符的UTF-8用户名或密码。将SASLprep应用于用户参数、PASS参数或APOP username参数时，兼容服务器或客户端必须将其视为查询字符串[RFC3454]。将SASLprep应用于APOP password参数时，兼容服务器或客户端必须将其视为存储字符串[RFC3454]。
If the server includes the USER argument in the UTF8 capability response, the client MAY use UTF-8 characters with a "USER", "PASS", or "APOP" command; the client MAY do so before issuing the "UTF8" command. Clients MUST NOT use UTF-8 characters when authenticating if the server did not include the USER argument in the UTF8 capability response.
如果服务器在UTF8功能响应中包含用户参数，则客户端可以将UTF-8字符与“USER”、“PASS”或“APOP”命令一起使用；客户端可以在发出“UTF8”命令之前执行此操作。如果服务器未在UTF8功能响应中包含用户参数，则客户端在进行身份验证时不得使用UTF-8字符。
The server MUST reject UTF-8 usernames or passwords that fail to comply with the formal syntax in UTF-8 [RFC3629].
服务器必须拒绝不符合UTF-8[RFC3629]中正式语法的UTF-8用户名或密码。
Use of UTF-8 strings in the "AUTH" command is governed by the POP3 SASL [RFC5034] mechanism.
“AUTH”命令中UTF-8字符串的使用由POP3 SASL[RFC5034]机制控制。
This document adds a new POP3 extension [RFC2449] capability response tag to indicate support for a new command: "LANG".
本文档添加了一个新的POP3扩展[RFC2449]功能响应标记，以表示对新命令的支持：“LANG”。
The capability tag and new command are described below.
下面描述了能力标签和新命令。
CAPA tag: LANG
卡帕标签：朗
Arguments with CAPA tag: none
带有CAPA标记的参数：无
Added Commands: LANG
添加命令：LANG
Standard commands affected: All
受影响的标准命令：全部
Announced states / possible differences: both / no
宣布的州/可能的差异：两者/否
Commands valid in states: AUTHORIZATION, TRANSACTION
在以下状态下有效的命令：授权、事务
Specification reference: this document
规范参考：本文件
POP3 allows most +OK and -ERR server responses to include human-readable text that, in some cases, might be presented to the user. But that text is limited to ASCII by the POP3 specification [RFC1939]. The "LANG" capability and command permit a POP3 client to negotiate which language the server uses when sending human-readable text.
POP3允许大多数+OK和-ERR服务器响应包含人类可读的文本，在某些情况下，这些文本可能会呈现给用户。但该文本受POP3规范[RFC1939]限制为ASCII。“LANG”功能和命令允许POP3客户端协商服务器在发送人类可读文本时使用的语言。
The "LANG" command requests that human-readable text included in all subsequent +OK and -ERR responses be localized to a language matching the language range argument (the "basic language range" as described by the "Matching of Language Tags" [RFC4647]). If the command succeeds, the server returns a +OK response followed by a single space, the exact language tag selected, and another space. Human-readable text in the appropriate language then appears in the rest of the line. This, and subsequent protocol-level human-readable text, is encoded in the UTF-8 charset.
“LANG”命令要求将所有后续+OK和-ERR响应中包含的人类可读文本本地化为与语言范围参数匹配的语言（“语言标记匹配”[RFC4647]所述的“基本语言范围”）。如果命令成功，服务器将返回+OK响应，后跟一个空格、选定的确切语言标记和另一个空格。然后，相应语言的人类可读文本将显示在该行的其余部分。该文本以及随后的协议级人类可读文本编码在UTF-8字符集中。
If the command fails, the server returns an -ERR response and subsequent human-readable response text continues to use the language that was previously used.
如果命令失败，服务器将返回-ERR响应，后续的人类可读响应文本将继续使用以前使用的语言。
If the client issues a "LANG" command with the special "*" language range argument, it indicates a request to use a language designated as preferred by the server administrator. The preferred language MAY vary based on the currently active user.
如果客户端发出带有特殊“*”语言范围参数的“LANG”命令，则表示请求使用服务器管理员指定的首选语言。首选语言可能因当前活动用户而异。
If no argument is given and the POP3 server issues a positive response, that response will usually consist of multiple lines. After the initial +OK, for each language tag the server supports, the POP3 server responds with a line for that language. This line is called a "language listing".
如果没有给出参数，并且POP3服务器发出肯定响应，则该响应通常由多行组成。在初始+OK之后，对于服务器支持的每个语言标记，POP3服务器都会用该语言的一行进行响应。这一行称为“语言列表”。
In order to simplify parsing, all POP3 servers are required to use a certain format for language listings. A language listing consists of the language tag [RFC5646] of the message, optionally followed by a single space and a human-readable description of the language in the language itself, using the UTF-8 charset. There is no specific order to the listing of languages; the order may depend on configuration or implementation.
为了简化解析，所有POP3服务器都需要使用特定的语言列表格式。语言列表由消息的语言标记[RFC5646]组成，可选地后跟一个空格，以及使用UTF-8字符集的语言本身的可读描述。语言清单没有具体的顺序；顺序可能取决于配置或实现。
Examples for "LANG" capability usage are shown below.
“LANG”功能使用示例如下所示。
Note that some examples do not include the correct character accents due to limitations of the RFC format.
请注意，由于RFC格式的限制，某些示例不包括正确的字符重音。
C: USER karen
S: +OK Hello, karen
C: PASS password
S: +OK karen's maildrop contains 2 messages (320 octets)
C: USER karen
S: +OK Hello, karen
C: PASS password
S: +OK karen's maildrop contains 2 messages (320 octets)
Client requests deprecated MUL language [ISO639-2]. Server replies with -ERR response.
客户端请求不推荐使用的MUL语言[ISO639-2]。服务器答复为-ERR响应。
C: LANG MUL
S: -ERR invalid language MUL
C: LANG MUL
S: -ERR invalid language MUL
A LANG command with no parameters is a request for a language listing.
不带参数的LANG命令是对语言列表的请求。
C: LANG
S: +OK Language listing follows:
S: en English
S: en-boont English Boontling dialect
S: de Deutsch
S: it Italiano
S: es Espanol
S: sv Svenska
S: .
C: LANG
S: +OK Language listing follows:
S: en English
S: en-boont English Boontling dialect
S: de Deutsch
S: it Italiano
S: es Espanol
S: sv Svenska
S: .
A request for a language listing might fail.
请求语言列表可能会失败。
C: LANG
S: -ERR Server is unable to list languages
C: LANG
S: -ERR Server is unable to list languages
Once the client selects the language, all responses will be in that language, starting with the response to the "LANG" command.
一旦客户端选择语言，所有响应都将使用该语言，从对“LANG”命令的响应开始。
C: LANG es
S: +OK es Idioma cambiado
C: LANG es
S: +OK es Idioma cambiado
If a server returns an -ERR response to a "LANG" command that specifies a primary language, the current language for responses remains in effect.
如果服务器对指定主语言的“LANG”命令返回-ERR响应，则响应的当前语言仍然有效。
C: LANG uga
S: -ERR es Idioma <<UGA>> no es conocido
C: LANG uga
S: -ERR es Idioma <<UGA>> no es conocido
C: LANG sv
S: +OK sv Kommandot "LANG" lyckades
C: LANG sv
S: +OK sv Kommandot "LANG" lyckades
C: LANG *
S: +OK es Idioma cambiado
C: LANG *
S: +OK es Idioma cambiado
When a POP3 server uses a native non-ASCII character maildrop, it is the responsibility of the server to comply with the POP3 base specification [RFC1939] and Internet Message Format [RFC5322] when not in UTF-8 mode. When the server is not in UTF-8 mode and the message requires that mode, requests to download the message MAY be rejected (as specified in the next section) or the various alternatives outlined in Section 2.1 above, including creation and delivery of surrogates for the original message, MAY be considered.
当POP3服务器使用本机非ASCII字符邮件投递时，服务器有责任在不处于UTF-8模式时遵守POP3基本规范[RFC1939]和互联网消息格式[RFC5322]。当服务器未处于UTF-8模式且消息需要该模式时，下载消息的请求可能会被拒绝（如下一节所述），或者可以考虑上文第2.1节所述的各种备选方案，包括为原始消息创建和交付代理。
Per "POP3 Extension Mechanism" [RFC2449], this document adds a new response code: UTF8, described below.
根据“POP3扩展机制”[RFC2449]，本文档添加了一个新的响应代码：UTF8，如下所述。
Complete response code: UTF8
完整响应代码：UTF8
Valid for responses: -ERR
对响应有效：-ERR
Valid for commands: LIST, TOP, RETR
对以下命令有效：LIST、TOP、RETR
Response code meaning and expected client behavior: The "UTF8" response code indicates that a failure is due to a request for message content that contains a UTF-8 string when the client is not in UTF-8 mode.
响应代码含义和预期的客户端行为：“UTF8”响应代码表示，当客户端未处于UTF-8模式时，由于请求包含UTF-8字符串的消息内容而导致失败。
The client MAY reissue the command after entering UTF-8 mode.
客户端可以在进入UTF-8模式后重新发出该命令。
Sections 2 and 3 of this specification update two capabilities ("UTF8" and "LANG") in the POP3 capability registry [RFC2449].
本规范第2节和第3节更新了POP3功能注册表[RFC2449]中的两个功能（“UTF8”和“LANG”）。
Section 5 of this specification adds one new response code ("UTF8") to the POP3 response codes registry [RFC2449].
本规范第5节向POP3响应代码注册表[RFC2449]添加了一个新的响应代码（“UTF8”）。
The security considerations of UTF-8 [RFC3629], SASLprep [RFC4013], and the Unicode Format for Network Interchange [RFC5198] apply to this specification, particularly with respect to use of UTF-8 strings in usernames and passwords.
UTF-8[RFC3629]、SASLprep[RFC4013]和网络交换Unicode格式[RFC5198]的安全注意事项适用于本规范，特别是在用户名和密码中使用UTF-8字符串方面。
The "LANG *" command might reveal the existence and preferred language of a user to an active attacker probing the system if the active language changes in response to the "USER", "PASS", or "APOP" commands prior to validating the user's credentials. Servers are strongly advised to implement a configuration to prevent this exposure.
“LANG*”命令可能会向探测系统的主动攻击者透露用户的存在和首选语言，如果主动语言在验证用户凭据之前响应“user”、“PASS”或“APOP”命令而发生变化。强烈建议服务器实施一种配置以防止这种暴露。
It is possible for a man-in-the-middle attacker to insert a "LANG" command in the command stream, thus, making protocol-level diagnostic responses unintelligible to the user. A mechanism to protect the
中间人攻击者有可能在命令流中插入“LANG”命令，从而使用户无法理解协议级诊断响应。保护环境的机制
integrity of the session can be used to defeat such attacks. For example, a client can issue the "STLS" command [RFC2595] before issuing the "LANG" command.
会话的完整性可用于击败此类攻击。例如，客户机可以在发出“LANG”命令之前发出“STLS”命令[RFC2595]。
As with other internationalization upgrades, modifications to server authentication code (in this case, to support non-ASCII strings) need to be done with care to avoid introducing vulnerabilities (for example, in string parsing or matching). This is particularly important if the native databases or mailstore of the operating system use some character set or encoding other than Unicode in UTF-8.
与其他国际化升级一样，对服务器身份验证代码的修改（在本例中，为支持非ASCII字符串）需要小心，以避免引入漏洞（例如，在字符串解析或匹配中）。如果操作系统的本机数据库或邮件存储使用UTF-8中的Unicode以外的字符集或编码，这一点尤为重要。
[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。
[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。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC2449] Gellens, R., Newman, C., and L. Lundblade, "POP3 Extension Mechanism", RFC 2449, November 1998.
[RFC2449]Gellens，R.，Newman，C.，和L.Lundblade，“POP3扩展机制”，RFC 2449，1998年11月。
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of Internationalized Strings ("stringprep")", RFC 3454, December 2002.
[RFC3454]Hoffman，P.和M.Blanchet，“国际化弦的准备（“stringprep”）”，RFC 3454，2002年12月。
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003.
[RFC3629]Yergeau，F.，“UTF-8，ISO 10646的转换格式”，STD 63，RFC 3629，2003年11月。
[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names and Passwords", RFC 4013, February 2005.
[RFC4013]Zeilenga，K.，“SASLprep：用户名和密码的Stringprep配置文件”，RFC40113，2005年2月。
[RFC4647] Phillips, A. and M. Davis, "Matching of Language Tags", BCP 47, RFC 4647, September 2006.
[RFC4647]Phillips，A.和M.Davis，“语言标记的匹配”，BCP 47，RFC 4647，2006年9月。
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network Interchange", RFC 5198, March 2008.
[RFC5198]Klensin，J.和M.Padlipsky，“网络交换的Unicode格式”，RFC 51982008年3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。
[RFC5646] Phillips, A. and M. Davis, "Tags for Identifying Languages", BCP 47, RFC 5646, September 2009.
[RFC5646]Phillips，A.和M.Davis，“识别语言的标记”，BCP 47，RFC 5646，2009年9月。
[RFC6152] Klensin, J., Freed, N., Rose, M., and D. Crocker, "SMTP Service Extension for 8-bit MIME Transport", STD 71, RFC 6152, March 2011.
[RFC6152]Klensin，J.，Freed，N.，Rose，M.，和D.Crocker，“8位MIME传输的SMTP服务扩展”，STD 71，RFC 6152，2011年3月。
[RFC6530] Klensin, J. and Y. Ko, "Overview and Framework for Internationalized Email", RFC 6530, February 2012.
[RFC6530]Klensin，J.和Y.Ko，“国际化电子邮件的概述和框架”，RFC6530，2012年2月。
[RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized Email Headers", RFC 6532, February 2012.
[RFC6532]Yang，A.，Steele，S.，和N.Freed，“国际化电子邮件标题”，RFC 6532，2012年2月。
[RFC6855] Resnick, P., Newman, C., and S. Shen, "IMAP Support for UTF-8", RFC 6855, March 2013.
[RFC6855]Resnick，P.，Newman，C.，和S.Shen，“UTF-8的IMAP支持”，RFC 68552013年3月。
[ISO639-2] International Organization for Standardization, "ISO 639-2:1998. Codes for the representation of names of languages -- Part 2: Alpha-3 code", October 1998.
[ISO639-2]国际标准化组织，“ISO 639-2:1998.语言名称表示代码——第2部分：阿尔法-3代码”，1998年10月。
[RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations", RFC 2231, November 1997.
[RFC2231]Freed，N.和K.Moore，“MIME参数值和编码字扩展：字符集、语言和连续体”，RFC 22311997年11月。
[RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC 2595, June 1999.
[RFC2595]Newman，C.，“将TLS与IMAP、POP3和ACAP一起使用”，RFC2595，1999年6月。
[RFC5034] Siemborski, R. and A. Menon-Sen, "The Post Office Protocol (POP3) Simple Authentication and Security Layer (SASL) Authentication Mechanism", RFC 5034, July 2007.
[RFC5034]Siemborski，R.和A.Menon Sen，“邮局协议（POP3）简单认证和安全层（SASL）认证机制”，RFC 5034，2007年7月。
[RFC5721] Gellens, R. and C. Newman, "POP3 Support for UTF-8", RFC 5721, February 2010.
[RFC5721]Gellens，R.和C.Newman，“UTF-8的POP3支持”，RFC 57212010年2月。
This non-normative section discusses the reasons behind some of the design choices in this specification.
本非规范性章节讨论了本规范中某些设计选择背后的原因。
Due to interoperability problems with the MIME Message Header Extensions [RFC2047] and limited deployment of the extended MIME parameter encodings [RFC2231], it is hoped these 7-bit encoding mechanisms can be deprecated in the future when UTF-8 header support becomes prevalent.
由于MIME消息头扩展[RFC2047]存在互操作性问题，并且扩展MIME参数编码[RFC2231]的部署有限，因此希望将来当UTF-8头支持变得普遍时，这些7位编码机制可能会被弃用。
The USER capability (Section 2.2) and hence the upgraded "USER" command and additional support for non-ASCII credentials, are optional because the implementation burden of SASLprep [RFC4013] is not well understood, and mandating such support in all cases could negatively impact deployment.
用户能力（第2.2节）以及因此升级的“用户”命令和对非ASCII凭证的额外支持是可选的，因为对SASLprep[RFC4013]的实现负担没有很好的理解，并且在所有情况下强制执行此类支持可能会对部署产生负面影响。
Thanks to John Klensin, Joseph Yee, Tony Hansen, Alexey Melnikov, and other Email Address Internationalization working group participants who provided helpful suggestions and interesting debate that improved this specification.
感谢John Klensin、Joseph Yee、Tony Hansen、Alexey Melnikov和其他电子邮件地址国际化工作组参与者，他们提供了有益的建议和有趣的辩论，改进了该规范。
Authors' Addresses
作者地址
Randall Gellens QUALCOMM Incorporated 5775 Morehouse Drive San Diego, CA 92651 USA
美国加利福尼亚州圣地亚哥Morehouse大道5775号兰德尔盖伦高通公司，邮编92651
EMail: rg+ietf@qualcomm.com
EMail: rg+ietf@qualcomm.com
Chris Newman Oracle 800 Royal Oaks Monrovia, CA 91016-6347 USA
美国加利福尼亚州蒙罗维亚皇家橡树园800号克里斯纽曼甲骨文91016-6347
EMail: chris.newman@oracle.com
EMail: chris.newman@oracle.com
Jiankang YAO CNNIC No.4 South 4th Street, Zhongguancun Beijing China
中国北京中关村南四街4号建康姚CNNIC
Phone: +86 10 58813007
EMail: yaojk@cnnic.cn
Phone: +86 10 58813007
EMail: yaojk@cnnic.cn
Kazunori Fujiwara Japan Registry Services Co., Ltd. Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda Tokyo Japan
藤原和仁日本注册服务有限公司日本东京西神田3-8-1号千代田第一大厦东13楼
Phone: +81 3 5215 8451
EMail: fujiwara@jprs.co.jp
Phone: +81 3 5215 8451
EMail: fujiwara@jprs.co.jp