draft-ietf-extra-sieve-special-use-00.txt		draft-ietf-extra-sieve-special-use-01.txt
	EXTRA S. Bosch		EXTRA S. Bosch
	Internet-Draft Dovecot Oy		Internet-Draft Dovecot Oy
	Intended status: Standards Track September 13, 2017		Intended status: Standards Track January 7, 2018
	Expires: March 17, 2018		Expires: July 11, 2018
	Sieve Email Filtering: Delivering to Special-Use Mailboxes		Sieve Email Filtering: Delivering to Special-Use Mailboxes
	draft-ietf-extra-sieve-special-use-00		draft-ietf-extra-sieve-special-use-01
	Abstract		Abstract
	The SPECIAL-USE capability of the IMAP protocol (RFC 6154) allows		The SPECIAL-USE capability of the IMAP protocol (RFC 6154) allows
	clients to identify special-use mailboxes; e.g., where draft or sent		clients to identify special-use mailboxes; e.g., where draft or sent
	messages should be put. This simplifies client configuration. In		messages should be put. This simplifies client configuration. In
	contrast, the Sieve mail filtering language (RFC 5228) currently has		contrast, the Sieve mail filtering language (RFC 5228) currently has
	no such capability. This memo defines a Sieve extension that fills		no such capability. This memo defines a Sieve extension that fills
	this gap: it adds a test for checking whether a special-use attribute		this gap: it adds a test for checking whether a special-use attribute
	is assigned for a particular mailbox or any mailbox, and it adds the		is assigned for a particular mailbox or any mailbox, and it adds the
	skipping to change at page 1, line 38 ¶		skipping to change at page 1, line 38 ¶
	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 17, 2018.		This Internet-Draft will expire on July 11, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2018 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
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	skipping to change at page 2, line 45 ¶		skipping to change at page 2, line 45 ¶
	SPECIAL-USE capability [SPECIAL-USE], IMAP clients can also configure		SPECIAL-USE capability [SPECIAL-USE], IMAP clients can also configure
	these attributes dynamically based on user preference.		these attributes dynamically based on user preference.
	Unlike the IMAP protocol, the Sieve mail filtering language [SIEVE]		Unlike the IMAP protocol, the Sieve mail filtering language [SIEVE]
	currently cannot freely access these special-use mailbox attributes.		currently cannot freely access these special-use mailbox attributes.
	Particularly, the Sieve interpreter cannot find an anonymous mailbox		Particularly, the Sieve interpreter cannot find an anonymous mailbox
	that has a particular special-use attribute assigned. This would be		that has a particular special-use attribute assigned. This would be
	very useful for example to find the user's Spam mailbox at delivery.		very useful for example to find the user's Spam mailbox at delivery.
	In Sieve, limited access to the special-use attributes is provided		In Sieve, limited access to the special-use attributes is provided
	using the "mboxmetadata" extension [MAILBOX], which allows testing		using the "mboxmetadata" extension [SIEVE-MAILBOX], which allows
	for the presence of a special-use attribute in the "/private/		testing for the presence of a special-use attribute in the "/private/
	specialuse" IMAP METADATA [IMAP-METADATA] entry of a mailbox. Still,		specialuse" IMAP METADATA [IMAP-METADATA] entry of a mailbox. Still,
	not all implementers will be willing to add the complexity of the		not all implementers will be willing to add the complexity of the
	IMAP METADATA capability, just to provide access to special-use		IMAP METADATA capability, just to provide access to special-use
	attributes to the Sieve interpreter.		attributes to the Sieve interpreter.
	This document defines an extension to the Sieve mail filtering		This document defines an extension to the Sieve mail filtering
	language that adds the ability to freely access mailbox special-use		language that adds the ability to freely access mailbox special-use
	attributes. It adds a test called "specialuse_exists" that checks		attributes. It adds a test called "specialuse_exists" that checks
	whether a special-use attribute is assigned for a particular mailbox		whether a special-use attribute is assigned for a particular mailbox
	or - if omitted - any mailbox. It also adds the ability to file		or - if omitted - any mailbox. It also adds the ability to file
	skipping to change at page 3, line 51 ¶		skipping to change at page 3, line 51 ¶
	a. the indicated mailbox exists,		a. the indicated mailbox exists,
	b. that mailbox allows the user in whose context the Sieve script		b. that mailbox allows the user in whose context the Sieve script
	runs to "deliver" messages into it, and		runs to "deliver" messages into it, and
	c. that mailbox has all of the special-use flags listed in the		c. that mailbox has all of the special-use flags listed in the
	"special-use-flags" argument assigned to it.		"special-use-flags" argument assigned to it.
	Refer to the specification of the "mailboxexists" test in Section 3.1		Refer to the specification of the "mailboxexists" test in Section 3.1
	of RFC 5490 [MAILBOX] for a definition of when "delivery" of messages		of RFC 5490 [SIEVE-MAILBOX] for a definition of when "delivery" of
	into a mailbox is deemed possible.		messages into a mailbox is deemed possible.
	4. ":specialuse" Argument to "fileinto" Command		4. ":specialuse" Argument to "fileinto" Command
	Usage: fileinto [:specialuse <special-use-flag: string>]		Usage: fileinto [:specialuse <special-use-flag: string>]
	<mailbox: string>		<mailbox: string>
	Normally, the "fileinto" command delivers the message in the mailbox		Normally, the "fileinto" command delivers the message in the mailbox
	specified using its positional mailbox argument. However, if the		specified using its positional mailbox argument. However, if the
	optional ":specialuse" argument is also specified, the "fileinto"		optional ":specialuse" argument is also specified, the "fileinto"
	command first checks whether a mailbox exists with the specified		command first checks whether a mailbox exists with the specified
	skipping to change at page 4, line 32 ¶		skipping to change at page 4, line 32 ¶
	o An anonymous special-use mailbox, which has at least the special-		o An anonymous special-use mailbox, which has at least the special-
	use flag specified with the ":specialuse" argument assigned to it.		use flag specified with the ":specialuse" argument assigned to it.
	o The default mailbox named by the positional string argument of the		o The default mailbox named by the positional string argument of the
	"fileinto" command, which is used when the special-use mailbox is		"fileinto" command, which is used when the special-use mailbox is
	not found.		not found.
	The special-use flag specified with the ":specialuse" argument MUST		The special-use flag specified with the ":specialuse" argument MUST
	conform to the "use-attr" syntax described in Section 6 of RFC6154		conform to the "use-attr" syntax described in Section 6 of RFC6154
	[MAILBOX]. Implementations SHOULD handle an invalid special-use flag		[SIEVE-MAILBOX]. Implementations SHOULD handle an invalid special-
	in the same way as an invalid mailbox name is handled. The string		use flag in the same way as an invalid mailbox name is handled. The
	parameter of the ":specialuse" argument is not a constant string,		string parameter of the ":specialuse" argument is not a constant
	which means that variable substitutions are allowed when the		string, which means that variable substitutions are allowed when the
	"variables" extension [VARIABLES] is active. In that case, the		"variables" extension [VARIABLES] is active. In that case, the
	syntax of the special-use flag is only verified at runtime.		syntax of the special-use flag is only verified at runtime.
	If neither the special-use mailbox nor the default mailbox exists,		If neither the special-use mailbox nor the default mailbox exists,
	the "fileinto" action MUST proceed exactly as it does in case the		the "fileinto" action MUST proceed exactly as it does in case the
	":specialuse" is argument is absent and the mailbox named by its		":specialuse" is argument is absent and the mailbox named by its
	positional argument does not exist. The various options for handling		positional argument does not exist. The various options for handling
	this situation are described in Section 4.1 of RFC5228 [SIEVE].		this situation are described in Section 4.1 of RFC5228 [SIEVE].
	More than one mailbox can have a particular special-use flag		More than one mailbox can have a particular special-use flag
	skipping to change at page 5, line 13 ¶		skipping to change at page 5, line 13 ¶
	to its existence, the Sieve interpreter MUST NOT subsequently attempt		to its existence, the Sieve interpreter MUST NOT subsequently attempt
	delivery in the indicated default mailbox as a fall-back. Instead,		delivery in the indicated default mailbox as a fall-back. Instead,
	it MUST proceed exactly as it does in case the ":specialuse" argument		it MUST proceed exactly as it does in case the ":specialuse" argument
	is absent and delivery to the mailbox named by its positional		is absent and delivery to the mailbox named by its positional
	argument fails. This prevents the situation where messages are		argument fails. This prevents the situation where messages are
	unexpectedly spread over two mailboxes in case transient or		unexpectedly spread over two mailboxes in case transient or
	intermittent delivery failures occur.		intermittent delivery failures occur.
	4.1. Interaction with ":create" Argument to "fileinto" Command		4.1. Interaction with ":create" Argument to "fileinto" Command
	The "mailbox" extension [MAILBOX] adds the optional ":create"		The "mailbox" extension [SIEVE-MAILBOX] adds the optional ":create"
	argument to the "fileinto" command. If the optional ":create"		argument to the "fileinto" command. If the optional ":create"
	argument is specified with "fileinto", it instructs the Sieve		argument is specified with "fileinto", it instructs the Sieve
	interpreter to create the specified mailbox if needed, before		interpreter to create the specified mailbox if needed, before
	attempting to deliver the message into the specified mailbox.		attempting to deliver the message into the specified mailbox.
	When combined with the ":specialuse" argument, the ":create" argument		When combined with the ":specialuse" argument, the ":create" argument
	instructs the Sieve interpreter to create the specified default		instructs the Sieve interpreter to create the specified default
	mailbox if needed. This need arises when both the special-use and		mailbox if needed. This need arises when both the special-use and
	the default mailbox are not found.		the default mailbox are not found.
	skipping to change at page 6, line 36 ¶		skipping to change at page 6, line 36 ¶
	}		}
	if allof(		if allof(
	environment "imap.cause" "COPY",		environment "imap.cause" "COPY",
	specialuse_exists "${mailbox}" "\\Junk") {		specialuse_exists "${mailbox}" "\\Junk") {
	redirect "spam-report@example.org";		redirect "spam-report@example.org";
	}		}
	7. Security Considerations		7. Security Considerations
	Security considerations are discussed in [SIEVE] and [SPECIAL-USE].		Security considerations are discussed in [SIEVE], [VARIABLES], and
	It is believed that this extension does not introduce any additional		[SPECIAL-USE]. It is believed that this extension does not introduce
	security concerns.		any additional security concerns.
	8. IANA Considerations		8. IANA Considerations
	The following template specifies the IANA registration of the Sieve		The following template specifies the IANA registration of the Sieve
	extension specified in this document:		extension specified in this document:
	To: iana@iana.org		To: iana@iana.org
	Subject: Registration of new Sieve extension		Subject: Registration of new Sieve extension
	Capability name: special-use		Capability name: special-use
	skipping to change at page 7, line 23 ¶		skipping to change at page 7, line 23 ¶
	mailbox that has a particular IMAP special-use		mailbox that has a particular IMAP special-use
	attribute assigned.		attribute assigned.
	RFC number: this RFC		RFC number: this RFC
	Contact address: Sieve mailing list <sieve@ietf.org>		Contact address: Sieve mailing list <sieve@ietf.org>
	This information should be added to the list of sieve extensions		This information should be added to the list of sieve extensions
	given on http://www.iana.org/assignments/sieve-extensions.		given on http://www.iana.org/assignments/sieve-extensions.
	9. Acknowledgements		9. Acknowledgements
	Thanks to Barry Leiba, Alexey Melnikov, Ken Murchison, and Ned Freed		Thanks to Stan Kalisch, Barry Leiba, Alexey Melnikov, Ken Murchison,
	for reviews and suggestions.		and Ned Freed for reviews and suggestions.
			Thanks to the authors of RFC5490 [SIEVE-MAILBOX] from which some
			descriptive text is borrowed in this document.
	10. References		10. References
	10.1. Normative References		10.1. Normative References
	[IMAP-METADATA]		[IMAP-METADATA]
	Daboo, C., "The IMAP METADATA Extension", RFC 5464, DOI		Daboo, C., "The IMAP METADATA Extension", RFC 5464,
	10.17487/RFC5464, February 2009,		DOI 10.17487/RFC5464, February 2009,
	<http://www.rfc-editor.org/info/rfc5464>.		<http://www.rfc-editor.org/info/rfc5464>.
	[KEYWORDS]		[KEYWORDS]
	Bradner, S., "Key words for use in RFCs to Indicate		Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[MAILBOX] Melnikov, A., "The Sieve Mail-Filtering Language --
	Extensions for Checking Mailbox Status and Accessing
	Mailbox Metadata", RFC 5490, March 2009.
	[SIEVE] Guenther, P. and T. Showalter, "Sieve: An Email Filtering		[SIEVE] Guenther, P. and T. Showalter, "Sieve: An Email Filtering
	Language", RFC 5228, January 2008.		Language", RFC 5228, January 2008.
			[SIEVE-MAILBOX]
			Melnikov, A., "The Sieve Mail-Filtering Language --
			Extensions for Checking Mailbox Status and Accessing
			Mailbox Metadata", RFC 5490, March 2009.
	[SPECIAL-USE]		[SPECIAL-USE]
	Leiba, B. and J. Nicolson, "IMAP LIST Extension for		Leiba, B. and J. Nicolson, "IMAP LIST Extension for
	Special-Use Mailboxes", RFC 6154, DOI 10.17487/RFC6154,		Special-Use Mailboxes", RFC 6154, DOI 10.17487/RFC6154,
	March 2011, <http://www.rfc-editor.org/info/rfc6154>.		March 2011, <http://www.rfc-editor.org/info/rfc6154>.
	[VARIABLES]		[VARIABLES]
	Homme, K., "Sieve Email Filtering: Variables Extension",		Homme, K., "Sieve Email Filtering: Variables Extension",
	RFC 5229, January 2008.		RFC 5229, January 2008.
	10.2. Informative References		10.2. Informative References
End of changes. 13 change blocks.
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