draft-ietf-eai-rfc5335bis-12.txt   draft-ietf-eai-rfc5335bis-13.txt 
Email Address Internationalization A. Yang Email Address Internationalization A. Yang
(EAI) TWNIC (EAI) TWNIC
Internet-Draft S. Steele Internet-Draft S. Steele
Obsoletes: 5335 (if approved) Microsoft Obsoletes: 5335 (if approved) Microsoft
Updates: 2045,5322 (if approved) N. Freed Updates: 2045 (if approved) N. Freed
Intended status: Standards Track Oracle Intended status: Standards Track Oracle
Expires: March 21, 2012 September 18, 2011 Expires: April 23, 2012 October 21, 2011
Internationalized Email Headers Internationalized Email Headers
draft-ietf-eai-rfc5335bis-12 draft-ietf-eai-rfc5335bis-13
Abstract Abstract
Internet mail was originally limited to 7-bit ASCII. MIME added Internet mail was originally limited to 7-bit ASCII. MIME added
support for the use of 8-bit character sets in body parts, and also support for the use of 8-bit character sets in body parts, and also
defined an encoded-word construct so other character sets could be defined an encoded-word construct so other character sets could be
used in certain header field values. But full internationalization used in certain header field values. But full internationalization
of electronic mail requires additional enhancements to allow the use of electronic mail requires additional enhancements to allow the use
of Unicode, including characters outside the ASCII repertoire, in of Unicode, including characters outside the ASCII repertoire, in
mail addresses as well as direct use of Unicode in header fields like mail addresses as well as direct use of Unicode in header fields like
From:, To:, and Subject:, without requiring the use of complex From:, To:, and Subject:, without requiring the use of complex
encoded-word constructs. This document specifies an enhancement to encoded-word constructs. This document specifies an enhancement to
the Internet Message Format that allows use of Unicode in mail the Internet Message Format and to MIME that allows use of Unicode in
addresses and most header field content. mail addresses and most header field content.
This specification replaces RFC 5335. This specification also
updates Section 6.4 of RFC 2045 to eliminate the restriction
prohibiting the use of non-identity content-transfer-encodings on
subtypes of "message/".
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 21, 2012. This Internet-Draft will expire on April 23, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 23 skipping to change at page 2, line 28
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology Used In This Specification . . . . . . . . . . . . 3 2. Terminology Used In This Specification . . . . . . . . . . . . 3
3. Changes to Message Header Fields . . . . . . . . . . . . . . . 4 3. Changes to Message Header Fields . . . . . . . . . . . . . . . 4
3.1. UTF-8 Syntax and Normalization . . . . . . . . . . . . . . 4 3.1. UTF-8 Syntax and Normalization . . . . . . . . . . . . . . 4
3.2. Syntax Extensions to RFC 5322 . . . . . . . . . . . . . . 5 3.2. Syntax Extensions to RFC 5322 . . . . . . . . . . . . . . 5
3.3. Use of 8-bit UTF-8 in Message-Ids . . . . . . . . . . . . 5 3.3. Use of 8-bit UTF-8 in Message-Ids . . . . . . . . . . . . 5
3.4. Effects on Line Length Limits . . . . . . . . . . . . . . 5 3.4. Effects on Line Length Limits . . . . . . . . . . . . . . 6
3.5. Changes to MIME Message Type Encoding Restrictions . . . . 6 3.5. Changes to MIME Message Type Encoding Restrictions . . . . 6
3.6. Use of MIME Encoded-Words . . . . . . . . . . . . . . . . 6 3.6. Use of MIME Encoded-Words . . . . . . . . . . . . . . . . 6
3.7. The Message/global Media Type . . . . . . . . . . . . . . 6 3.7. The Message/global Media Type . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
7. Edit history . . . . . . . . . . . . . . . . . . . . . . . . . 9 7. Edit history . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. draft-ietf-eai-rfc5335bis-00 . . . . . . . . . . . . . . . 9 7.1. draft-ietf-eai-rfc5335bis-00 . . . . . . . . . . . . . . . 9
7.2. draft-ietf-eai-rfc5335bis-01 . . . . . . . . . . . . . . . 10 7.2. draft-ietf-eai-rfc5335bis-01 . . . . . . . . . . . . . . . 10
7.3. draft-ietf-eai-rfc5335bis-02 . . . . . . . . . . . . . . . 10 7.3. draft-ietf-eai-rfc5335bis-02 . . . . . . . . . . . . . . . 10
7.4. draft-ietf-eai-rfc5335bis-03 . . . . . . . . . . . . . . . 10 7.4. draft-ietf-eai-rfc5335bis-03 . . . . . . . . . . . . . . . 10
7.5. draft-ietf-eai-rfc5335bis-04 . . . . . . . . . . . . . . . 10 7.5. draft-ietf-eai-rfc5335bis-04 . . . . . . . . . . . . . . . 10
7.6. draft-ietf-eai-rfc5335bis-05 . . . . . . . . . . . . . . . 10 7.6. draft-ietf-eai-rfc5335bis-05 . . . . . . . . . . . . . . . 10
7.7. draft-ietf-eai-rfc5335bis-06 . . . . . . . . . . . . . . . 10 7.7. draft-ietf-eai-rfc5335bis-06 . . . . . . . . . . . . . . . 10
7.8. draft-ietf-eai-rfc5335bis-07 . . . . . . . . . . . . . . . 10 7.8. draft-ietf-eai-rfc5335bis-07 . . . . . . . . . . . . . . . 10
7.9. draft-ietf-eai-rfc5335bis-09 . . . . . . . . . . . . . . . 10 7.9. draft-ietf-eai-rfc5335bis-09 . . . . . . . . . . . . . . . 11
7.10. draft-ietf-eai-rfc5335bis-10 . . . . . . . . . . . . . . . 11 7.10. draft-ietf-eai-rfc5335bis-10 . . . . . . . . . . . . . . . 11
7.11. draft-ietf-eai-rfc5335bis-11 . . . . . . . . . . . . . . . 11 7.11. draft-ietf-eai-rfc5335bis-11 . . . . . . . . . . . . . . . 11
7.12. draft-ietf-eai-rfc5335bis-12 . . . . . . . . . . . . . . . 11 7.12. draft-ietf-eai-rfc5335bis-12 . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.13. draft-ietf-eai-rfc5335bis-13 . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
Internet mail distinguishes a message from its transport and further Internet mail distinguishes a message from its transport and further
divides a message between a header and a body [RFC5598]. Internet divides a message between a header and a body [RFC5322]. Internet
mail header field values contain a variety of strings that are mail header field values contain a variety of strings that are
intended to be user-visible. The range of supported characters for intended to be user-visible. The range of supported characters for
these strings was originally limited to 7-bit [ASCII]. MIME these strings was originally limited to 7-bit [ASCII]. MIME
[RFC2045] [RFC2046] [RFC2047] provides the ability to use additional [RFC2045] [RFC2046] [RFC2047] provides the ability to use additional
character sets, but this support is limited to body part data and to character sets, but this support is limited to body part data and to
special encoded-word constructs that were only allowed in a limited special encoded-word constructs that were only allowed in a limited
number of places in header field values. number of places in header field values.
Globalization of the Internet requires support of the much larger set Globalization of the Internet requires support of the much larger set
of characters provided by Unicode [RFC5198] in both mail addresses of characters provided by Unicode [RFC5198] in both mail addresses
skipping to change at page 3, line 41 skipping to change at page 3, line 41
on having non-identity content-transfer-encodings on any subtype of on having non-identity content-transfer-encodings on any subtype of
the message top-level type so that message/global parts can be safely the message top-level type so that message/global parts can be safely
transmitted across existing mail infrastructure. transmitted across existing mail infrastructure.
This specification is based on a model of native, end-to-end support This specification is based on a model of native, end-to-end support
for UTF-8, which depends on having an "8-bit clean" environment for UTF-8, which depends on having an "8-bit clean" environment
assured by the transport system. Support for carriage across legacy, assured by the transport system. Support for carriage across legacy,
7-bit infrastructure and for processing by 7-bit receivers requires 7-bit infrastructure and for processing by 7-bit receivers requires
additional mechanisms that are not provided by these specifications. additional mechanisms that are not provided by these specifications.
This specification is a revision of and replacement for [RFC5335].
Section 6 of [I-D.ietf-eai-frmwrk-4952bis] describes the change in
approach between this specification and the previous version.
2. Terminology Used In This Specification 2. Terminology Used In This Specification
A plain ASCII string is fully compatible with [RFC5321] and A plain ASCII string is fully compatible with [RFC5321] and
[RFC5322]. In this document, non-ASCII strings are UTF-8 strings if [RFC5322]. In this document, non-ASCII strings are UTF-8 strings if
they are in header field values which contain at least one <UTF8-non- they are in header field values which contain at least one <UTF8-non-
ascii> (see Section 3.1). ascii> (see Section 3.1).
Unless otherwise noted, all terms used here are defined in [RFC5321], Unless otherwise noted, all terms used here are defined in [RFC5321],
[RFC5322], [I-D.ietf-eai-frmwrk-4952bis], or [RFC5322], [I-D.ietf-eai-frmwrk-4952bis], or
[I-D.ietf-eai-rfc5336bis]. [I-D.ietf-eai-rfc5336bis].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
The term "8-bit" means octets are present in the data with values The term "8-bit" means octets are present in the data with values
above 0x7F. above 0x7F.
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sections specify the necessary changes to RFC 5322's ABNF. sections specify the necessary changes to RFC 5322's ABNF.
The syntax rules not mentioned below remain defined as in [RFC5322]. The syntax rules not mentioned below remain defined as in [RFC5322].
Note that this protocol does not change RFC 5322 rules for defining Note that this protocol does not change RFC 5322 rules for defining
header field names. The bodies of header fields are allowed to header field names. The bodies of header fields are allowed to
contain Unicode characters, but the header field names themselves contain Unicode characters, but the header field names themselves
must contain only ASCII characters. must contain only ASCII characters.
Also note that messages in this format require the use of the Also note that messages in this format require the use of the
&UTF8SMTPbis; extension [I-D.ietf-eai-rfc5336bis] to be transferred UTF8SMTPbis extension [I-D.ietf-eai-rfc5336bis] to be transferred via
via SMTP. SMTP.
3.1. UTF-8 Syntax and Normalization 3.1. UTF-8 Syntax and Normalization
UTF-8 characters can be defined in terms of octets using the UTF-8 characters can be defined in terms of octets using the
following ABNF [RFC5234], taken from [RFC3629]: following ABNF [RFC5234], taken from [RFC3629]:
UTF8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4 UTF8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4
UTF8-2 = <Defined in Section 4 of RFC3629> UTF8-2 = <Defined in Section 4 of RFC3629>
UTF8-3 = <Defined in Section 4 of RFC3629> UTF8-3 = <Defined in Section 4 of RFC3629>
UTF8-4 = <Defined in Section 4 of RFC3629> UTF8-4 = <Defined in Section 4 of RFC3629>
See [RFC5198] for a discussion of Unicode normalization; See [RFC5198] for a discussion of Unicode normalization;
normalization form [NFC] SHOULD be used. Actually, if one is going normalization form NFC [UNF] SHOULD be used. Actually, if one is
to do internationalization properly, one of the most often-cited going to do internationalization properly, one of the most often-
goals is to permit people to spell their names correctly. Since many cited goals is to permit people to spell their names correctly.
mailbox local parts reflect personal names, that principle applies to Since many mailbox local parts reflect personal names, that principle
mailboxes as well. The NFKC normalization form SHOULD NOT be used applies to mailboxes as well. The NFKC normalization form [UNF]
because it may lose information that is needed to correctly spell SHOULD NOT be used because it may lose information that is needed to
some names in some unusual circumstances. correctly spell some names in some unusual circumstances.
3.2. Syntax Extensions to RFC 5322 3.2. Syntax Extensions to RFC 5322
The following rules extend the ABNF syntax defined in [RFC5322] and The following rules extend the ABNF syntax defined in [RFC5322] and
[RFC5234] in order to allow UTF-8 content. [RFC5234] in order to allow UTF-8 content.
VCHAR =/ UTF8-non-ascii VCHAR =/ UTF8-non-ascii
ctext =/ UTF8-non-ascii ctext =/ UTF8-non-ascii
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4. Domains. 4. Domains.
Note that header field names are not on this list; these are still Note that header field names are not on this list; these are still
restricted to ASCII. restricted to ASCII.
3.3. Use of 8-bit UTF-8 in Message-Ids 3.3. Use of 8-bit UTF-8 in Message-Ids
Implementers of message-id generation algorithms MAY prefer to Implementers of message-id generation algorithms MAY prefer to
restrain their output to ASCII since that has some advantages, such restrain their output to ASCII since that has some advantages, such
as when constructing References fields in mailing-list threads where as when constructing In-reply-to: and References: header fields in
some senders use EAI and others not. mailing-list threads where some senders use EAI and others not.
3.4. Effects on Line Length Limits 3.4. Effects on Line Length Limits
Section 2.1.1 of [RFC5322] limits lines to 998 characters and Section 2.1.1 of [RFC5322] limits lines to 998 characters and
recommends that the lines be restricted to only 78 characters. This recommends that the lines be restricted to only 78 characters. This
specification changes the former limit to 988 octets. (Note that in specification changes the former limit to 998 octets. (Note that in
ASCII octets and characters are effectively the same but this is not ASCII octets and characters are effectively the same but this is not
true in UTF-8.) The 78 character limit remains defined in terms of true in UTF-8.) The 78 character limit remains defined in terms of
characters, not octets, since it is intended to address display width characters, not octets, since it is intended to address display width
issues, not line length issues. issues, not line length issues.
3.5. Changes to MIME Message Type Encoding Restrictions 3.5. Changes to MIME Message Type Encoding Restrictions
This specification updates Section 6.4 of [RFC2045]. [RFC2045] This specification updates Section 6.4 of [RFC2045]. [RFC2045]
prohibits applying a content-transfer-encoding to any subtypes of prohibits applying a content-transfer-encoding to any subtypes of
"message/". This specification relaxes that rule -- it allows newly "message/". This specification relaxes that rule -- it allows newly
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Background: Normally, transfer of message/global will be done in Background: Normally, transfer of message/global will be done in
8-bit-clean channels, and body parts will have "identity" encodings, 8-bit-clean channels, and body parts will have "identity" encodings,
that is, no decoding is necessary. that is, no decoding is necessary.
But in the case where a message containing a message/global is But in the case where a message containing a message/global is
downgraded from 8-bit to 7-bit as described in [RFC6152], an encoding downgraded from 8-bit to 7-bit as described in [RFC6152], an encoding
might have to be applied to the message; if the message travels might have to be applied to the message; if the message travels
multiple times between a 7-bit environment and an environment multiple times between a 7-bit environment and an environment
implementing these extensions, multiple levels of encoding may occur. implementing these extensions, multiple levels of encoding may occur.
This is expected to be rarely seen in practice, and the potential This is expected to be rarely seen in practice, and the potential
complexity of other ways of dealing with the issue are thought to be complexity of other ways of dealing with the issue is thought to be
larger than the complexity of allowing nested encodings where larger than the complexity of allowing nested encodings where
necessary. necessary.
3.6. Use of MIME Encoded-Words 3.6. Use of MIME Encoded-Words
The MIME encoded-words facility [RFC2047] provides the ability to The MIME encoded-words facility [RFC2047] provides the ability to
place non-ASCII text, but only in a subset of the places allowed by place non-ASCII text, but only in a subset of the places allowed by
this extension. Additionally, encoded-words are substantially more this extension. Additionally, encoded-words are substantially more
complex since they allow the use of arbitrary charsets. Accordingly, complex since they allow the use of arbitrary charsets. Accordingly,
encoded-words SHOULD NOT be used when generating header fields for encoded-words SHOULD NOT be used when generating header fields for
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global message" if: global message" if:
o it contains 8-bit UTF-8 header values as specified in this o it contains 8-bit UTF-8 header values as specified in this
document, or document, or
o it contains 8-bit UTF-8 values in the header fields of body parts. o it contains 8-bit UTF-8 values in the header fields of body parts.
The content of a message/global part is otherwise identical to that The content of a message/global part is otherwise identical to that
of a message/rfc822 part. of a message/rfc822 part.
If this type is sent to a 7-bit-only system, it has to have an If an object of this type is sent to a 7-bit-only system, it MUST
appropriate content-transfer-encoding applied. (Note that a system have an appropriate content-transfer-encoding applied. (Note that a
compliant with MIME that doesn't recognize message/global is supposed system compliant with MIME that doesn't recognize message/global is
to treat it as "application/octet-stream" as described in Section supposed to treat it as "application/octet-stream" as described in
5.2.4 of [RFC2046].) Section 5.2.4 of [RFC2046].)
Type name: message Type name: message
Subtype name: global Subtype name: global
Required parameters: none Required parameters: none
Optional parameters: none Optional parameters: none
Encoding considerations: Any content-transfer-encoding is permitted. Encoding considerations: Any content-transfer-encoding is permitted.
The 8-bit or binary content-transfer-encodings are recommended The 8-bit or binary content-transfer-encodings are recommended
where permitted. where permitted.
Security considerations: See Section 4. Security considerations: See Section 4.
Interoperability considerations: This media type provides Interoperability considerations: This media type provides
functionality similar to the message/rfc822 content type for email functionality similar to the message/rfc822 content type for email
messages with international email headers. When there is a need messages with internationalized email headers. When there is a
to embed or return such content in another message, there is need to embed or return such content in another message, there is
generally an option to use this media type and leave the content generally an option to use this media type and leave the content
unchanged or down-convert the content to message/rfc822. Both of unchanged or down-convert the content to message/rfc822. Both of
these choices will interoperate with the installed base, but with these choices will interoperate with the installed base, but with
different properties. Systems unaware of internationalized different properties. Systems unaware of internationalized
headers will typically treat a message/global body part as an headers will typically treat a message/global body part as an
unknown attachment, while they will understand the structure of a unknown attachment, while they will understand the structure of a
message/rfc822. However, systems that understand message/global message/rfc822. However, systems that understand message/global
will provide functionality superior to the result of a down- will provide functionality superior to the result of a down-
conversion to message/rfc822. The most interoperable choice conversion to message/rfc822. The most interoperable choice
depends on the deployed software. depends on the deployed software.
Published specification: RFC XXXX Published specification: RFC XXXX
Applications that use this media type: SMTP servers and email Applications that use this media type: SMTP servers and email
clients that support multipart/report generation or parsing. clients that support multipart/report generation or parsing.
Email clients that forward messages with international headers as Email clients that forward messages with internationalized headers
attachments. as attachments.
Additional information: Additional information:
Magic number(s): none Magic number(s): none
File extension(s): The extension ".u8msg" is suggested. File extension(s): The extension ".u8msg" is suggested.
Macintosh file type code(s): A uniform type identifier (UTI) of Macintosh file type code(s): A uniform type identifier (UTI) of
"public.utf8-email-message" is suggested. This conforms to "public.utf8-email-message" is suggested. This conforms to
"public.message" and "public.composite-content", but does not "public.message" and "public.composite-content", but does not
necessarily conform to "public.utf8-plain-text". necessarily conform to "public.utf8-plain-text".
Person & email address to contact for further information: See the Person & email address to contact for further information: See the
Author's Address section of this document. Author's Address section of this document.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: This is a structured media type that embeds Restrictions on usage: This is a structured media type that embeds
other MIME media types. The 8-bit or binary content-transfer- other MIME media types. An 8-bit or binary content-transfer-
encoding SHOULD be used unless this media type is sent over a encoding SHOULD be used unless this media type is sent over a
7-bit-only transport. 7-bit-only transport.
Author: See the Author's Address section of this document. Author: See the Author's Address section of this document.
Change controller: IETF Standards Process Change controller: IETF Standards Process
4. Security Considerations 4. Security Considerations
Because UTF-8 often requires several octets to encode a single Because UTF-8 often requires several octets to encode a single
skipping to change at page 9, line 4 skipping to change at page 9, line 6
998 octets, excluding the CRLF. On the other hand, MDA (Mail 998 octets, excluding the CRLF. On the other hand, MDA (Mail
Delivery Agent) processes that parse, store, or handle email Delivery Agent) processes that parse, store, or handle email
addresses or local parts must take extra care not to overflow addresses or local parts must take extra care not to overflow
buffers, truncate addresses, or exceed storage allotments. Also, buffers, truncate addresses, or exceed storage allotments. Also,
they must take care, when comparing, to use the entire lengths of the they must take care, when comparing, to use the entire lengths of the
addresses. addresses.
There are lots of ways to use UTF-8 to represent something equivalent There are lots of ways to use UTF-8 to represent something equivalent
or similar to a particular displayed character or group of or similar to a particular displayed character or group of
characters; see the security considerations in [RFC3629] for details characters; see the security considerations in [RFC3629] for details
on the problems this can cause. The normalization process is on the problems this can cause. The normalization process described
described in Section 3.1 is recommended to minimize these issues. in Section 3.1 is recommended to minimize these issues.
The security impact of UTF-8 headers on email signature systems such The security impact of UTF-8 headers on email signature systems such
as Domain Keys Identified Mail (DKIM), S/MIME, and OpenPGP is as Domain Keys Identified Mail (DKIM), S/MIME, and OpenPGP is
discussed in [I-D.ietf-eai-frmwrk-4952bis], Section 14. discussed in [I-D.ietf-eai-frmwrk-4952bis], Section 14.
If a user has a non-ASCII mailbox address and an ASCII mailbox If a user has a non-ASCII mailbox address and an ASCII mailbox
address, a digital certificate that identifies that user might have address, a digital certificate that identifies that user might have
both addresses in the identity. Having multiple email addresses as both addresses in the identity. Having multiple email addresses as
identities in a single certificate is already supported in PKIX identities in a single certificate is already supported in PKIX
(Public Key Infrastructure for X.509 Certificates) [RFC5280] and (Public Key Infrastructure for X.509 Certificates) [RFC5280] and
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This document incorporates many ideas first described in Internet- This document incorporates many ideas first described in Internet-
Draft form by Paul Hoffman, although many details have changed from Draft form by Paul Hoffman, although many details have changed from
that earlier work. that earlier work.
The author especially thanks Jeff Yeh for his efforts and The author especially thanks Jeff Yeh for his efforts and
contributions on editing previous versions. contributions on editing previous versions.
Most of the content of this document was provided by John C Klensin Most of the content of this document was provided by John C Klensin
and Dave Crocker. Significant comments and suggestions were received and Dave Crocker. Significant comments and suggestions were received
from Charles H. Lindsey, Kari Hurtta, Pete Resnick, Alexey Melnikov, from Martin Duerst, Julien Elie, Arnt Gulbrandsen, Kristin Hubner,
Chris Newman, Kristin Hubner, Yangwoo Ko, Yoshiro Yoneya, and other Kari Hurtta, Yangwoo Ko, Charles H. Lindsey, Alexey Melnikov, Chris
members of the JET team (Joint Engineering Team) and were Newman, Pete Resnick, Yoshiro Yoneya, and additional members of the
incorporated into the document. The editors wish to sincerely thank JET team (Joint Engineering Team) and were incorporated into the
them all for their contributions. document. The editors wish to sincerely thank them all for their
contributions.
7. Edit history 7. Edit history
[[RFC Editor: please remove this section before publishing.]] [[RFC Editor: Please remove this section before publishing.]]
7.1. draft-ietf-eai-rfc5335bis-00 7.1. draft-ietf-eai-rfc5335bis-00
1. Applied Errata suggested by Alfred Hoenes. 1. Applied Errata suggested by Alfred Hoenes.
2. Adjust [RFC2821] and [RFC2822] to [RFC5321] and [RFC5322]. 2. Adjust [RFC2821] and [RFC2822] to [RFC5321] and [RFC5322].
3. Abrogate <alt-address> in ABNF of <angle-addr>. 3. Abrogate <alt-address> in ABNF of <angle-addr>.
4. Revoke [RFC5504] from this document. 4. Revoke [RFC5504] from this document.
5. Upgrade some references from I-Ds to RFC. 5. Upgrade some references from I-Ds to RFC.
skipping to change at page 11, line 38 skipping to change at page 11, line 44
discussion in RFC 3629. discussion in RFC 3629.
3. Added a section on the effects on line length limits. 3. Added a section on the effects on line length limits.
4. Removed the syntax restriction on the use of 8-bit UTF-8 in 4. Removed the syntax restriction on the use of 8-bit UTF-8 in
message-ids. message-ids.
5. Added text recommending that 8-bit UTF-8 be avoided in message- 5. Added text recommending that 8-bit UTF-8 be avoided in message-
ids. ids.
7.13. draft-ietf-eai-rfc5335bis-13
1. Updated and alphabetized the contributor list.
2. Corrected various typos, reworded some sections to make them
clearer.
3. Replaced the reference to RFC 5598 with a reference to RFC 5322.
4. Removed the Updates: RFC 5322. RFC 5322 is extended by this
document, not updated.
5. Added some text to the Introduction referring to the framework
document for information about changes between this specification
and RFC 5335.
6. Added text to the Abstract to say that this document replaces RFC
5335 and that RFC 2045 is updated.
8. References 8. References
8.1. Normative References 8.1. Normative References
[ASCII] "Coded Character Set -- 7-bit American [ASCII] "Coded Character Set -- 7-bit American
Standard Code for Information Standard Code for Information
Interchange", ANSI X3.4, 1986. Interchange", ANSI X3.4, 1986.
[I-D.ietf-eai-frmwrk-4952bis] Klensin, J. and Y. Ko, "Overview and [I-D.ietf-eai-frmwrk-4952bis] Klensin, J. and Y. Ko, "Overview and
Framework for Internationalized Framework for Internationalized
Email", Email",
draft-ietf-eai-frmwrk-4952bis-10 (work draft-ietf-eai-frmwrk-4952bis-10 (work
in progress), September 2010. in progress), September 2010.
[I-D.ietf-eai-rfc5336bis] Yao, J. and W. MAO, "SMTP Extension [I-D.ietf-eai-rfc5336bis] Yao, J. and W. MAO, "SMTP Extension
for Internationalized Email Address", for Internationalized Email Address",
draft-ietf-eai-rfc5336bis-07 (work in draft-ietf-eai-rfc5336bis-07 (work in
progress), December 2010. progress), December 2010.
[NFC] Davis, M. and K. Whistler, "Unicode
Standard Annex #15: Unicode
Normalization Forms", September 2010,
<http://www.unicode.org/reports/
tr15/>.
[RFC2119] Bradner, S., "Key words for use in [RFC2119] Bradner, S., "Key words for use in
RFCs to Indicate Requirement Levels", RFCs to Indicate Requirement Levels",
BCP 14, RFC 2119, March 1997. BCP 14, RFC 2119, March 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation [RFC3629] Yergeau, F., "UTF-8, a transformation
format of ISO 10646", STD 63, format of ISO 10646", STD 63,
RFC 3629, November 2003. RFC 3629, November 2003.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode [RFC5198] Klensin, J. and M. Padlipsky, "Unicode
Format for Network Interchange", Format for Network Interchange",
skipping to change at page 12, line 36 skipping to change at page 13, line 8
[RFC5234] Crocker, D. and P. Overell, "Augmented [RFC5234] Crocker, D. and P. Overell, "Augmented
BNF for Syntax Specifications: ABNF", BNF for Syntax Specifications: ABNF",
STD 68, RFC 5234, January 2008. STD 68, RFC 5234, January 2008.
[RFC5321] Klensin, J., "Simple Mail Transfer [RFC5321] Klensin, J., "Simple Mail Transfer
Protocol", RFC 5321, October 2008. Protocol", RFC 5321, October 2008.
[RFC5322] Resnick, P., Ed., "Internet Message [RFC5322] Resnick, P., Ed., "Internet Message
Format", RFC 5322, October 2008. Format", RFC 5322, October 2008.
[RFC5598] Crocker, D., "Internet Mail [UNF] Davis, M. and K. Whistler, "Unicode
Architecture", RFC 5598, July 2009. Standard Annex #15: Unicode
Normalization Forms", September 2010,
<http://www.unicode.org/reports/
tr15/>.
8.2. Informative References 8.2. Informative References
[RFC2045] Freed, N. and N. Borenstein, [RFC2045] Freed, N. and N. Borenstein,
"Multipurpose Internet Mail Extensions "Multipurpose Internet Mail Extensions
(MIME) Part One: Format of Internet (MIME) Part One: Format of Internet
Message Bodies", RFC 2045, Message Bodies", RFC 2045,
November 1996. November 1996.
[RFC2046] Freed, N. and N. Borenstein, [RFC2046] Freed, N. and N. Borenstein,
skipping to change at page 13, line 21 skipping to change at page 13, line 43
and T. Roessler, "MIME Security with and T. Roessler, "MIME Security with
OpenPGP", RFC 3156, August 2001. OpenPGP", RFC 3156, August 2001.
[RFC5280] Cooper, D., Santesson, S., Farrell, [RFC5280] Cooper, D., Santesson, S., Farrell,
S., Boeyen, S., Housley, R., and W. S., Boeyen, S., Housley, R., and W.
Polk, "Internet X.509 Public Key Polk, "Internet X.509 Public Key
Infrastructure Certificate and Infrastructure Certificate and
Certificate Revocation List (CRL) Certificate Revocation List (CRL)
Profile", RFC 5280, May 2008. Profile", RFC 5280, May 2008.
[RFC5335] Abel, Y., "Internationalized Email
Headers", RFC 5335, September 2008.
[RFC6152] Klensin, J., Freed, N., Rose, M., and [RFC6152] Klensin, J., Freed, N., Rose, M., and
D. Crocker, "SMTP Service Extension D. Crocker, "SMTP Service Extension
for 8-bit MIME Transport", STD 71, for 8-bit MIME Transport", STD 71,
RFC 6152, March 2011. RFC 6152, March 2011.
Authors' Addresses Authors' Addresses
Abel Yang Abel Yang
TWNIC TWNIC
4F-2, No. 9, Sec 2, Roosevelt Rd. 4F-2, No. 9, Sec 2, Roosevelt Rd.
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