One document matched: draft-ietf-imapext-i18n-13.txt
Differences from draft-ietf-imapext-i18n-12.txt
Network Working Group Chris Newman
Internet-Draft Sun Microsystems
Intended Status: Proposed Standard Arnt Gulbrandsen
Oryx Mail Systems GmhH
Alexey Melnikov
Isode Limited
November 14, 2007
Internet Message Access Protocol Internationalization
draft-ietf-imapext-i18n-13.txt
Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
Internet Message Access Protocol (IMAP) version 4rev1 has basic
support for non-ASCII characters in mailbox names and search
substrings. It also supports non-ASCII message headers and content
encoded as specified by Multipurpose Internet Mail Extensions
(MIME). This specification defines a collection of IMAP extensions
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which improve international support including comparator negotiation
for search, sort and thread, language negotiation for international
error text, and translations for namespace prefixes.
Table of Contents
1. Conventions Used in this Document . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LANGUAGE Extension . . . . . . . . . . . . . . . . . . . . . 3
3.1 LANGUAGE Extension Requirements . . . . . . . . . . . . . . . 3
3.2 LANGUAGE Command . . . . . . . . . . . . . . . . . . . . . . 4
3.3 LANGUAGE Response . . . . . . . . . . . . . . . . . . . . . . 6
3.4 TRANSLATION Extension to the NAMESPACE Response . . . . . . . 6
3.5 Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 6
4. COMPARATOR Extension . . . . . . . . . . . . . . . . . . . . 7
4.1 COMPARATOR Extension Requirements . . . . . . . . . . . . . . 8
4.2 Comparators and Charsets . . . . . . . . . . . . . . . . . . 9
4.3 COMPARATOR Command . . . . . . . . . . . . . . . . . . . . . 9
4.4 COMPARATOR Response . . . . . . . . . . . . . . . . . . . . . 10
4.5 Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Other IMAP Internationalization Issues . . . . . . . . . . . 11
5.1 UTF-8 Userids and Passwords . . . . . . . . . . . . . . . . . 11
5.2 UTF-8 Mailbox Names . . . . . . . . . . . . . . . . . . . . . 11
5.3 UTF-8 Domains, Addresses and Mail Headers . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
9. Relevant Standards for i18n IMAP Implementations . . . . . . 13
Normative References . . . . . . . . . . . . . . . . . . . . 13
Informative References . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . 16
Conventions Used in This Document
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 [RFC2119].
The formal syntax use the Augmented Backus-Naur Form (ABNF)
[RFC4234] notation including the core rules defined in Appendix A.
The UTF8-related productions are defined in [RFC3629].
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
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editorial clarity only and are not part of the actual protocol
exchange.
2. Introduction
This specification defines two IMAP4rev1 [RFC3501] extensions to
enhance international support. These extensions can be advertised
and implemented separately.
The LANGUAGE extension allows the client to request a suitable
language for protocol error messages and in combination with the
NAMESPACE extension [RFC2342] enables namespace translations.
The COMPARATOR extension allows the client to request a suitable
collation which will modify the behavior of the base specification's
SEARCH command as well as the SORT and THREAD extensions [SORT].
This leverages the collation registry [RFC4790].
3. LANGUAGE Extension
IMAP allows server responses to include human-readable text that in
many cases needs to be presented to the user. But that text is
limited to US-ASCII by the IMAP specification [RFC3501] in order to
preserve backwards compatibility with deployed IMAP implementations.
This section specifies a way for an IMAP client to negotiate which
language the server should use when sending human-readable text.
The LANGUAGE extension only provides a mechanism for altering fixed
server strings such as response text and NAMESPACE folder names.
Assigning localized language aliases to shared mailboxes would be
done with a separate mechanism such as the proposed METADATA
extension (see [METADATA]).
3.1 LANGUAGE Extension Requirements
IMAP servers that support this extension MUST list the keyword
LANGUAGE in their CAPABILITY response as well as in the greeting
CAPABILITY data.
A server that advertises this extension MUST use the language "i-
default" as described in [RFC2277] as its default language until
another supported language is negotiated by the client. A server
MUST include "i-default" as one of its supported languages.
Clients and servers that support this extension MUST also support
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the NAMESPACE extension [RFC2342].
The LANGUAGE command is valid in all states. Clients are urged to
issue LANGUAGE before authentication, since some servers send
valuable user information as part of authentication (e.g. "password
is correct, but expired").
3.2 LANGUAGE Command
Arguments: Optional language range arguments.
Response: A possible LANGUAGE response (see section 3.3).
A possible NAMESPACE response (see section 3.4).
Result: OK - Command completed
NO - Could not complete command
BAD - arguments invalid
The LANGUAGE command requests that human-readable text emitted by
the server be localized to a language matching one of the language
range argument as described by section 2 of [RFC4647].
If the command succeeds, the server will return human-readable
responses in the first supported language specified. These
responses will be in UTF-8 [RFC3629]. The server MUST send a
LANGUAGE response specifying the language used, and the change takes
effect immediately after the LANGUAGE response.
If the command fails, the server continues to return human-readable
responses in the language it was previously using.
The special "default" language range argument 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.
If a language range does not match a known language tag exactly but
does match a language by the rules of [RFC4647], the server MUST
send an untagged LANGUAGE response indicating the language selected.
If there aren't any arguments, the server SHOULD send an untagged
LANGUAGE response listing the languages it supports. If the server
is unable to enumerate the list of languages it supports it MAY
return a tagged NO response to the enumeration request.
< The server defaults to using English i-default responses until
the user explicitly changes the language. >
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C: A001 LOGIN KAREN PASSWORD
S: A001 OK LOGIN completed
< Client requested MUL language, which no server supports. >
C: A002 LANGUAGE MUL
S: A002 NO Unsupported language MUL
< A LANGUAGE command with no arguments is a request to enumerate
the list of languages the server supports. >
C: A003 LANGUAGE
S: * LANGUAGE (EN DE IT i-default)
S: A003 OK Supported languages have been enumerated
C: B001 LANGUAGE
S: B001 NO Server is unable to enumerate supported languages
< Once the client changes the language, all responses will be in
that language starting after the LANGUAGE response. Note that
this includes the NAMESPACE response. Because RFCs are in US-
ASCII, this document uses an ASCII transcription rather than
UTF-8 text, e.g. ue in the word "ausgefuehrt" >
C: C001 LANGUAGE DE
S: * LANGUAGE (DE)
S: * NAMESPACE (("" "/")) (("Other Users/" "/" "TRANSLATION"
("Andere Ben&APw-tzer/"))) (("Public Folders/" "/"
"TRANSLATION" ("Gemeinsame Mailboxen/")))
S: C001 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt
< If a server does not support the requested primary language,
responses will continue to be returned in the current language
the server is using. >
C: D001 LANGUAGE FR
S: D001 NO Diese Sprache ist nicht unterstuetzt
C: D002 LANGUAGE DE-IT
S: * LANGUAGE (DE-IT)
S: * NAMESPACE (("" "/"))(("Other Users/" "/" "TRANSLATION"
("Andere Ben&APw-tzer/"))) (("Public Folders/" "/"
"TRANSLATION" ("Gemeinsame Mailboxen/")))
S: D002 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt
C: D003 LANGUAGE "default"
S: * LANGUAGE (DE)
S: D003 OK Sprachwechsel durch LANGUAGE-Befehl ausgefuehrt
< Server does not speak French, but does speak English. User
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speaks Canadian French and Canadian English. >
C: E001 LANGUAGE FR-CA EN-CA
S: * LANGUAGE (EN)
S: E001 OK Now speaking English
3.3 LANGUAGE Response
Contents: A list of one or more language tags.
The LANGUAGE response occurs as a result of a LANGUAGE command. A
LANGUAGE response with a list containing a single language tag
indicates that the server is now using that language. A LANGUAGE
response with a list containing multiple language tags indicates the
server is communicating a list of available languages to the client,
and no change in the active language has been made.
3.4 TRANSLATION Extension to the NAMESPACE Response
If localized representations of the namespace prefixes are available
in the selected language, the server SHOULD include these in the
TRANSLATION extension to the NAMESPACE response.
The TRANSLATION extension to the NAMESPACE response returns a single
string, containing the modified UTF-7 [RFC3501] encoded translation
of the namespace prefix. It is the responsibility of the client to
convert between the namespace prefix and the translation of the
namespace prefix when presenting mailbox names to the user.
In this example a server supports the IMAP4 NAMESPACE command. It
uses no prefix to the user's Personal Namespace, a prefix of "Other
Users" to its Other Users' Namespace and a prefix of "Public
Folders" to its only Shared Namespace. Since a client will often
display these prefixes to the user, the server includes a
translation of them that can be presented to the user.
C: A001 LANGUAGE DE-IT
S: * NAMESPACE (("" "/")) (("Other Users/" "/" "TRANSLATION"
("Andere Ben&APw-tzer/"))) (("Public Folders/" "/"
"TRANSLATION" ("Gemeinsame Mailboxen/")))
S: A001 OK LANGUAGE-Befehl ausgefuehrt
3.5 Formal Syntax
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The following syntax specification inherits ABNF [RFC4234] rules
from IMAP4rev1 [RFC3501], IMAP4 Namespace [RFC2342], Tags for the
Identifying Languages [RFC4646], UTF-8 [RFC3629] and Collected
Extensions to IMAP4 ABNF [RFC4466].
command-any =/ language-cmd
; LANGUAGE command is valid in all states
language-cmd = "LANGUAGE" *(SP lang-range-quoted)
response-payload =/ language-data
language-data = "LANGUAGE" SP "(" lang-tag-quoted *(SP
lang-tag-quoted) ")"
namespace-trans = SP DQUOTE "TRANSLATION" DQUOTE SP "(" string ")"
; the string is encoded in Modified UTF-7.
; this is a subset of the syntax permitted by
; the Namespace-Response-Extension rule in [RFC4466]
lang-range-quoted = astring
; Once any literal wrapper or quoting is removed, this
; follows the language-range rule in [RFC4647]
lang-tag-quoted = astring
; Once any literal wrapper or quoting is removed, this follows
; the Language-Tag rule in [RFC4646]
resp-text = ["[" resp-text-code "]" SP ] UTF8-TEXT-CHAR
*(UTF8-TEXT-CHAR / "[")
; After the server is changed to a language other than
; i-default, this resp-text rule replaces the resp-text
; rule from [RFC3501].
UTF8-TEXT-CHAR = %x20-5A / %x5C-7E / UTF8-2 / UTF8-3 / UTF8-4
; UTF-8 excluding 7-bit control characters and "["
4. COMPARATOR Extension
IMAP4rev1 [RFC3501] includes the SEARCH command which can be used to
locate messages matching criteria including human-readable text.
The SORT extension [SORT] to IMAP allows the client to ask the
server to determine the order of messages based on criteria
including human-readable text. These mechanisms require the ability
to support non-English search and sort functions.
This section defines an IMAP extension to negotiate use of
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comparators [RFC4790] to internationalize IMAP SEARCH, SORT and
THREAD. The IMAP extension consists of a new command to determine
or change the active comparator and a new response to indicate the
active comparator and possibly other available comparators.
The term "default comparator" refers to the comparator which is used
by SEARCH and SORT absent any negotiation using the COMPARATOR
command. The term "active comparator" refers to the comparator
which will be used within a session e.g. by SEARCH and SORT. The
COMPARATOR command is used to change the active comparator.
The active comparator applies to the following SEARCH keys: "BCC",
"BODY", "CC", "FROM", "SUBJECT", "TEXT", "TO" and "HEADER". If the
server also advertises the "SORT" extension, then the active
comparator applies to the following SORT keys: "CC", "FROM",
"SUBJECT" and "TO". If the server advertises THREAD=ORDEREDSUBJECT,
then the active comparator applies to the ORDEREDSUBJECT threading
algorithm. If the server advertises THREAD=REFERENCES, then the
active comparator applies to the subject field comparisons done by
REFERENCES threading algorithm. Future extensions may choose to
apply the active comparator to their SEARCH keys.
For SORT and THREAD, the pre-processing necessary to extract the
base subject text from a Subject header occurs prior to the
application of a comparator.
4.1 COMPARATOR Extension Requirements
IMAP servers that support this extension MUST list the keyword
COMPARATOR in their CAPABILITY data once IMAP enters authenticated
state, and MAY list that keyword in other states.
A server that advertises this extension MUST implement the
i;unicode-casemap comparator, as defined in [UCM]. It MAY implement
other comparators from the IANA registry established by [RFC4790].
A server that advertises this extension SHOULD use i;unicode-casemap
as the default comparator. The selection of the default comparator
MAY be adjustable by the server administrator, and MAY be sensitive
to the current user. Once the IMAP connection enters authenticated
state, the default comparator MUST remain static for the remainder
of that connection.
A server that advertises this extension MUST support UTF-8 as a
SEARCH charset.
The COMPARATOR command is valid in authenticated and selected
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states.
Note that since SEARCH uses the substring operation, IMAP servers
can only implement collations that offer the substring operation
(see [RFC4790 section 4.2.2). Since SORT uses ordering operation
(and by implication equality), IMAP servers which advertise the SORT
extension can only implement collations that offer all three
operations (see [RFC4790] sections 4.2.2-4).
If the active collation does not provide the operations needed by an
IMAP command, the server MUST respond with a tagged BAD.
4.2 Comparators and Character Encodings
RFC 3501, section 6.4.4 says:
In all search keys that use strings, a message matches
the key if the string is a substring of the field. The
matching is case-insensitive.
When performing the SEARCH operation, the active comparator is
applied instead of the case-insensitive matching specified above.
An IMAP server which performs collation operations (e.g., as part of
commands such as SEARCH, SORT, THREAD) does so according to the
following procedure:
(a) MIME encoding (for example see [RFC2047] for headers and
[RFC2045] for body parts) MUST be removed in the texts being
collated.
If MIME encoding removal fails for a message (e.g., a body part
of the message has an unsupported Content-Transfer-Encoding,
uses characters not allowed by the Content-Transfer-Encoding,
etc.), the collation of this message is undefined by this
specification, and is handled in an implementation-dependent
manner.
(b) The decoded text from (a) MUST be converted to the charset
expected by the active comparator.
(c) For the substring operation:
If step (b) failed (e.g., the text is in an unknown charset,
contains a sequence which is not valid according in that
charset, etc.), the original decoded text from (a) (i.e.,
before the charset conversion attempt) is collated using the
i;octet comparator (see [RFC4790]).
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If step (b) was successful, the converted text from (b) is
collated according to the active comparator.
For the ordering operation:
All strings that were successfully converted by step (b) are
separated from all strings that failed step (b). Strings in
each group are collated independently. All strings that fail
step (b) are collated (after applying step (a)) using the
i;octet comparator (see [RFC4790]). All strings successfully
converted by step (b) are collated using the active comparator.
The resulting sorted list is produced by appending all collated
"failed" strings after all strings collated using the active
comparator.
<<Add an example>>
If the substring operation (e.g., IMAP SEARCH) of the active
comparator returns the "undefined" result (see section 4.2.3 of
[RFC4790]) for either the text specified in the SEARCH command or
the message text, then the operation is repeated on the result of
step (a) using the i;octet comparator.
The ordering operation (e.g., IMAP SORT and THREAD) SHOULD collate
the following together: strings encoded using unknown or invalid
character encodings, strings in unrecognized charsets, and invalid
input (as defined by the active collation).
4.3 COMPARATOR Command
Arguments: Optional comparator order arguments.
Response: A possible COMPARATOR response (see Section 4.4).
Result: OK - Command completed
NO - No matching comparator found
BAD - arguments invalid
The COMPARATOR command is used to determine or change the active
comparator. When issued with no arguments, it results in a
COMPARATOR response indicating the currently active comparator.
When issued with one or more comparator argument, it changes the
active comparator as directed. (If more than one installed
comparator is matched by an argument, the first argument wins.) The
COMPARATOR response lists all matching comparators if more than one
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matches the specified patterns.
The argument "default" refers to the server's default comparator.
Otherwise each argument is an collation specification as defined in
the Internet Application Protocol Comparator Registry [RFC4790].
< The client requests activating a Czech comparator if possible,
or else a generic international comparator which it considers
suitable for Czech. The server picks the first supported
comparator. >
C: A001 COMPARATOR "cz;*" i;basic
S: * COMPARATOR i;basic
S: A001 OK Will use i;basic for collation
4.4 COMPARATOR Response
Contents: The active comparator.
An optional list of available matching comparators
The COMPARATOR response occurs as a result of a COMPARATOR command.
The first argument in the comparator response is the name of the
active comparator. The second argument is a list of comparators
which matched any of the arguments to the COMPARATOR command and is
present only if more than one match is found.
4.5 Formal Syntax
The following syntax specification inherits ABNF [RFC4234] rules
from IMAP4rev1 [RFC3501], and Internet Application Protocol
Comparator Registry [RFC4790].
command-auth =/ comparator-cmd
resp-text-code =/ "BADCOMPARATOR" / "BADMATCH"
comparator-cmd = "COMPARATOR" *(SP comp-order-quoted)
response-payload =/ comparator-data
comparator-data = "COMPARATOR" SP comp-sel-quoted [SP "("
comp-id-quoted *(SP comp-id-quoted) ")"]
comp-id-quoted = astring
; Once any literal wrapper or quoting is removed, this
; follows the collation-id rule from [RFC4790]
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comp-order-quoted = astring
; Once any literal wrapper or quoting is removed, this
; follows the collation-order rule from [RFC4790]
comp-sel-quoted = astring
; Once any literal wrapper or quoting is removed, this
; follows the collation-selected rule from [RFC4790]
4.6 UNICASEMAP Extension Requirements
An IMAP server that implements the i;unicode-casemap comparator
[UCM] and satisfies all requirements specified in sections 4, 4.1
and 4.2 of this document, but doesn't implement the COMPARATOR
command and response, SHOULD advertise the UNICASEMAP capability in
the CAPABILITY response.
5. Other IMAP Internationalization Issues
The following sections provide an overview of various other IMAP
internationalization issues. These issues are not resolved by this
specification, but could be resolved by other standards work, such
as that being done by the EAI group (see [IMAP-EAI]).
5.1 Unicode Userids and Passwords
IMAP4rev1 presently restricts the userid and password fields of the
LOGIN command to US-ASCII. The "userid" and "password" fields of the
IMAP LOGIN command are restricted to US-ASCII only until a future
standards track RFC states otherwise. Servers are encouraged to
validate both fields to make sure they conform to the formal syntax
of UTF-8 and to reject the LOGIN command if that syntax is violated.
Servers MAY reject the use of any 8-bit in the "userid" or
"password" field.
When AUTHENTICATE is used, some servers may support userids and
passwords in Unicode [RFC3490] since SASL (see [RFC4422]) allows
that. However, such userids cannot be used as part of email
addresses.
5.2 UTF-8 Mailbox Names
The modified UTF-7 mailbox naming convention described in section
5.1.3 of RFC 3501 is best viewed as an transition from the status
quo in 1996 when modified UTF-7 was first specified. At that time,
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there was widespread unofficial use of local character sets such as
ISO-8859-1 and Shift-JIS for non-ASCII mailbox names, with resultant
non-interoperability.
The requirements in section 5.1 of RFC 3501 are very important if
we're ever going to be able to deploy UTF-8 mailbox names. Servers
are encouraged to enforce them.
5.3 UTF-8 Domains, Addresses and Mail Headers
There is now an IETF standard for Internationalizing Domain Names in
Applications [RFC3490]. While IMAP clients are free to support this
standard, an argument can be made that it would be helpful to simple
clients if the IMAP server could perform this conversion (the same
argument would apply to MIME header encoding [RFC2047]). However,
it would be unwise to move forward with such work until the work in
progress to define the format of international email addresses is
complete.
6. IANA Considerations
The IANA is requested to add LANGUAGE, COMPARATOR and UNICASEMAP to
the IMAP4 Capabilities Registry. [Note to IANA:
http://www.iana.org/assignments/imap4-capabilities]
7. Security Considerations
The LANGUAGE extension makes a new command available in "Not
Authenticated" state in IMAP. Some IMAP implementations run with
root privilege when the server is in "Not Authenticated" state and
do not revoke that privilege until after authentication is complete.
Such implementations are particularly vulnerable to buffer overflow
security errors at this stage and need to implement parsing of this
command with extra care.
A LANGUAGE command issued prior to activation of a security layer is
subject to an active attack which suppresses or modifies the
negotiation and thus makes STARTTLS or authentication error messages
more difficult to interpret. This is not a new attack as the error
messages themselves are subject to active attack. Clients MUST re-
issue the LANGUAGE command once a security layer is active, so this
does not impact subsequent protocol operations.
Both the LANGUAGE and COMPARATOR extensions use the UTF-8 charset,
thus the security considerations for UTF-8 [RFC3629] are relevent.
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However, neither uses UTF-8 for identifiers so the most serious
concerns do not apply.
8. Acknowledgements
The LANGUAGE extension is based on a previous Internet draft by Mike
Gahrns and Alexey Melnikov, a substantial portion of the text in
that section was written by them. Many people have participated in
discussions about an IMAP Language extension in the various fora of
the IETF and Internet working groups, so any list of contributors is
bound to be incomplete. However, the authors would like to thank
Andrew McCown for early work on the original proposal, John Myers
for suggestions regarding the namespace issue, along with Jutta
Degener, Mark Crispin, Mark Pustilnik, Larry Osterman, Cyrus Daboo
and Martin Duerst for their many suggestions that have been
incorporated into this document.
Initial discussion of the COMPARATOR extension involved input from
Mark Crispin and other participants of the IMAP Extensions WG.
9. Relevant Standards for i18n IMAP Implementations
This is a non-normative list of standards to consider when
implementing i18n aware IMAP software.
o The LANGUAGE and COMPARATOR extensions to IMAP (this
specification).
o The 8-bit rules for mailbox naming in section 5.1 of RFC 3501.
o The Mailbox International Naming Convention in section 5.1.3 of
RFC 3501.
o MIME [RFC2045] for message bodies.
o MIME header encoding [RFC2047] for message headers.
o The IETF EAI working group.
o MIME Parameter Value and Encoded Word Extensions [RFC2231] for
filenames. Quality IMAP server implementations will
automatically combine multipart parameters when generating the
BODYSTRUCTURE. There is also some deployed non-standard use of
MIME header encoding inside double-quotes for filenames.
o IDNA [RFC3490] and punycode [RFC3492] for domain names
(presently only relevant to IMAP clients).
o The UTF-8 charset [RFC3629].
o The IETF policy on Character Sets and Languages [RFC2277].
Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2277] Alvestrand, "IETF Policy on Character Sets and
Languages", BCP 18, RFC 2277, January 1998.
[RFC2342] Gahrns, Newman, "IMAP4 Namespace", RFC 2342, May 1998.
[RFC3501] Crispin, "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003.
[RFC3629] Yergeau, "UTF-8, a transformation format of ISO 10646",
STD 63, RFC 3629, November 2003.
[RFC4234] Crocker, Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, Brandenburg
Internetworking, Demon Internet Ltd, October 2005.
[RFC4422] Melnikov, Zeilenga, "Simple Authentication and Security
Layer (SASL)", RFC 4422, June 2006.
[RFC4466] Melnikov, Daboo, "Collected Extensions to IMAP4 ABNF",
RFC 4466, Isode Ltd., April 2006.
[RFC4646] Philips, Davis, "Tags for Identifying Languages", BCP 47,
RFC 4646, September 2006.
[RFC4647] Philips, Davis, "Matching of Language Tags", BCP 47, RFC
4647, September 2006.
[RFC4790] Newman, Duerst, Gulbrandsen, "Internet Application
Protocol Comparator Registry", RFC 4790, February 2007
[SORT] Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS
PROTOCOL - SORT AND THREAD EXTENSION", draft-ietf-
imapext-sort-19 (work in progress), November 2006.
[UCM] Crispin, "i;unicode-casemap - Simple Unicode Collation
Algorithm", RFC 5051, October 2007.
[RFC2045] Freed, Borenstein, "Multipurpose Internet Mail Extensions
(MIME) Part One: Format of Internet Message Bodies", RFC
2045, November 1996.
[RFC2047] Moore, "MIME (Multipurpose Internet Mail Extensions) Part
Three: Message Header Extensions for Non-ASCII Text", RFC
2047, November 1996.
Newman, Gulbrandsen Expires May 2008 FF[Page 15]
Internet-draft November 2007
Informative References
[RFC2231] Freed, Moore, "MIME Parameter Value and Encoded Word
Extensions: Character Sets, Languages, and
Continuations", RFC 2231, November 1997.
[RFC3490] Faltstrom, Hoffman, Costello, "Internationalizing Domain
Names in Applications (IDNA)", RFC 3490, March 2003.
[RFC3492] Costello, "Punycode: A Bootstring encoding of Unicode for
Internationalized Domain Names in Applications (IDNA)",
RFC 3492, March 2003.
[METADATA] Daboo, C., "IMAP METADATA Extension", draft-daboo-imap-
annotatemore-11 (work in progress), November 2006.
[IMAP-EAI] Resnick, Newman, "IMAP Support for UTF-8", draft-ietf-
eai-imap-utf8 (work in progress), May 2006.
Authors' Addresses
Chris Newman
Sun Microsystems
3401 Centrelake Dr., Suite 410
Ontario, CA 91761
US
Email: chris.newman@sun.com
Arnt Gulbrandsen
Oryx Mail Systems GmbH
Schweppermannstr. 8
D-81671 Muenchen
Germany
Email: arnt@oryx.com
Fax: +49 89 4502 9758
Alexey Melnikov
Isode Limited
5 Castle Business Village, 36 Station Road,
Hampton, Middlesex, TW12 2BX, UK
Newman, Gulbrandsen Expires May 2008 FF[Page 16]
Internet-draft November 2007
Email: Alexey.Melnikov@isode.com
Newman, Gulbrandsen Expires May 2008 FF[Page 17]
Internet-draft November 2007
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