Network Working Group M. Duerst
Internet-Draft Aoyama Gakuin University
Updates: XXXX (if approved) February 18, 2008
Intended status: Experimental
Expires: August 21, 2008
An update to the mailto URI scheme for Email Address
Internationalization
draft-ietf-eai-mailto-00
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document updates the definition of the mailto: URI Scheme for
use with internationalized email addresses.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Syntax of a mailto URI . . . . . . . . . . . . . . . . . . . . 3
3. Deployment . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Examples Using UTF-8-Based Percent-Encoding . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 7
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1. Introduction
[RFCXXXX] defines the mailto URI scheme. It allows for the encoding
of non-ASCII characters in arbitrary header fields and in the right-
hand side of email addresses, but not in the left-hand side of email
addresses. This document experimentally extends the syntax of
mailto: URIs to allow the encoding of non-ASCII characters on the
left-hand side of email addresses, and the designation of fallback
addresses. It also defines the mapping of mailto: URIs to email
messages using EAI features.
In order to keep this memo short and to reduce accidental
differences, where possible this memo does not repeat the provisions
in [RFCXXXX]. Whenever this memo does not specify something
different, the provisions in [RFCXXXX] MUST be followed.
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in [RFC2119].
Please send comments on this document to the mailing list
ima@ietf.org.
2. Syntax of a mailto URI
The syntax of the mailto URI given in [RFCXXXX] is changed to use the
"mailbox" production in [RFCYYYY] instead of [RFC2822]. Following
the syntax conventions of [STD66], and using the ABNF syntax defined
in [RFC5234], a "mailto" URI has the form:
mailtoURI = "mailto:" [ to ] [ headers ]
to = [ mailbox *("%2C" mailbox ) ]
headers = "?" header *( "&" header )
header = hname "=" hvalue
hname = *urlc
hvalue = *urlc
"mailbox" is as specified in [RFCYYYY], i.e. it is a mail address,
possibly including "phrase" and "comment" components. It also
possibly includes the alt-address component of angle-addr as
specified in [RFCYYYY]. However, the following changes apply:
1. All characters that can appear in "mailbox" but are reserved or
not allowed in URIs have to be percent-encoded. Examples are
parentheses, commas, the less-than and greater-than signs ("<"
and ">") and the percent sign ("%"), which commonly occur in the
"mailbox" syntax.
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2. Percent-encoding can be used to denote non-ASCII characters, in
order to denote an internationalized email address. Before
applying percent-encoding, it has to be made sure that the email
address is encoded in UTF-8 [STD63]. This makes the mailto URI
directly usable with EAI [RFC4952] and makes it compatible with
IRIs [RFC3987].
"hname" is an encoding of an [RFC2822] header name. "hvalue" is an
encoding of a [RFCYYYY] header value. As with "to", all URI reserved
characters must be encoded.
Non-ASCII characters can be encoded in "hvalue" as follows:
1. Non-ASCII characters SHOULD be encoded by first encoing the
characters according to UTF-8 [STD63], and then encoding each
octet of the corresponding UTF-8 octet sequence using percent-
encoding, to result in URI characters. This makes the mailto URI
directly usable with EAI [RFC4952] and makes it compatible with
IRIs [RFC3987].
2. MIME encoded words (as defined in [RFC2047]) MAY be used in
header values, but MUST NOT be used in an hvalue of a "body"
hname.
3. Deployment
For the forseeable future, URIs conforming to this memo should only
be used in contexts where it can be expected that the recipient can
create email messages conforming to the EAI framework [RFC4952].
4. Examples
4.1. Examples Using UTF-8-Based Percent-Encoding
Sending a mail to the user "coffee" (in French, i.e. "cafe" where the
final e is an e-acute) at the mailhost "natto".example.org ("natto"
is Japanese, written with the two Unicode characters U+7D0D and
U+8C46).
mailto:%3Ccaf%C3%A9@%E7%B4%8D%E8%B1%86.example.org%3E
Please note that if the left-hand side of the mail address contains
non-ASCII characters, the less-than and greater-than sign (angle
brackets, escaped as %3C and %3E) are mandatory.
The above example, with an "alt-address" (see [RFCYYYY])added:
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mailto:%3Ccaf%C3%A9@%E7%B4%8D%E8%B1%86.example.org%20%3Ccafe@
natto.example.org%3E%3E
Please note that at least a space is needed before the "alt-address",
and that such a space also has to be percent-encoded. Also, please
note that the URI above is separated into two lines to conform to
formatting conventions, but that there is no line bleak in actual
use.
5. Security Considerations
The security considerations of [RFCXXXX], [RFCYYYY], and [RFC4952]
apply, please read them carefully. There are no known security
threats specific to this memo alone.
6. IANA Considerations
This document updates the definition of the mailto: URI scheme; in
the registry of URI schemes, a reference to this memo should be added
to the current reference.
7. Acknowledgments
This document is the product of the EAI WG of the IETF. We thank all
the members of this WG.
8. Normative References
[RFC2047] Moore, K., "MIME Part Three: Message Header Extensions for
Non-ASCII Text", RFC 2047, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2822] Resnik, P., "Internet Message Format", RFC 2822,
April 2001.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", RFC 4952, July 2007.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
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Specifications: ABNF", STD 68, RFC 5234, November 1997.
[RFCXXXX] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto'
URI Scheme (work in progress)", January 2008.
[RFCYYYY] Abel, Y., "Internationalized Email Headers (work in
progress)", February 2008.
[STD63] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[STD66] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, April 2004.
Author's Address
Martin Duerst (Note: Please write "Duerst" with u-umlaut wherever
possible, for example as "Dürst" in XML and HTML.)
Aoyama Gakuin University
5-10-1 Fuchinobe
Sagamihara, Kanagawa 229-8558
Japan
Phone: +81 42 759 6329
Fax: +81 42 759 6495
Email: mailto:duerst@it.aoyama.ac.jp
URI: http://www.sw.it.aoyama.ac.jp/D%C3%BCrst/
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