EXTRA B. Gondwana, Ed.
Internet-Draft FastMail
Updates: 7162 (if approved) August 11, 2018
Intended status: Standards Track
Expires: February 12, 2019
Sieve Email Filtering: delivery by mailboxid
draft-gondwana-sieve-mailboxid-00
Abstract
The OBJECTID capability of the IMAP protocol (I-D.ietf-extra-imap-
objectid) allows clients to identify mailboxes by a unique identifier
which survives rename. In contrast, the Sieve mail filtering
language (RFC 5228) currently has no such capability. This memo
defines a Sieve extension that fills this gap: it adds a method for
specifying the unique identifier of a mailbox as a target for
fileinto rules, and a method for testing the existence of a mailbox
by its unique identifier.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used In This Document . . . . . . . . . . . . . . 2
3. Capability argument . . . . . . . . . . . . . . . . . . . . . 3
4. Argument ":mailboxid" to Command "fileinto" . . . . . . . . . 3
5. Test ":mailboxidexists" . . . . . . . . . . . . . . . . . . . 3
6. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 4
7. Security considerations . . . . . . . . . . . . . . . . . . . 4
8. IANA considerations . . . . . . . . . . . . . . . . . . . . . 4
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
10. TODO . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
11.1. Normative References . . . . . . . . . . . . . . . . . . 5
11.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Sieve rules are sometimes created using graphical interfaces which
allow users to select the mailbox to be used as a target for a rule.
If that mailbox is renamed, the client may also update its internal
representation of the rule and update the sieve script to match,
however this is a multi-step process and subject to partial failures.
Also, if the folder is renamed by a different mechanism (e.g. another
IMAP client) the rules will get out of sync.
By extending "fileinto" to reference an immutable mailboxid, sieve
rules can continue to target the same mailbox, regardless of how it
gets renamed.
2. Conventions Used In This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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3. Capability argument
The server must advertise the capability "mailboxid", and scripts
which use the following extensions must explicitly request the
capability "mailboxid".
Example:
require "mailboxid";
4. Argument ":mailboxid" to Command "fileinto"
Normally, the positional mailbox argument to a fileinto action
delivers the message in a mailbox with the matching [RFC3501] name.
This document adds a new tagged argument ":mailboxid". If the
":mailboxid" argument is provided, the positional mailbox argument
refers to an [I-D.ietf-extra-imap-objectid] mailboxid rather than an
[RFC3501] name.
If there is no mailbox with the specified ":mailboxid" then the
action is the same as if there was no named mailbox, and
implementations are free to make the same choices given in [RFC5228]
Section 4.1 when the specified mailbox doesn't exist.
The tagged argument ":mailboxid" to fileinto consumes zero additional
tokens.
Example:
require "fileinto";
require "mailboxid";
if header :contains ["from"] "coyote" {
fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3";
}
5. Test ":mailboxidexists"
This test behaves identically to the "mailboxexists" test defined in
[RFC5490] but operates on mailboxids rather than mailbox names.
Usage: "mailboxidexists <mailboxids: string-list>"
The "mailboxidexists" test is true if all mailboxes listed in the
"mailboxids" argument exist in the mailstore, and each allows the
user in whose context the Sieve script runs to "deliver" messages
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into it. When the mailstore is an IMAP server, "delivery" of
messages is possible if:
a) the READ-WRITE response code is present for the mailbox (see
Section 7.1 of [RFC3501]), if IMAP Access Control List (ACL)
[RFC4314] is not supported by the server, or
b) the user has 'p' or 'i' rights for the mailbox (see Section 5.2 of
[RFC4314]).
Note that a successful "mailboxidexists" test for a mailbox doesn't
necessarily mean that a "fileinto :mailboxid" action on this mailbox
would succeed. For example, the "fileinto" action might put user
over quota. The "mailboxidexists" only verifies existence of the
mailbox and whether the user in whose context the Sieve script runs
has permissions to execute "fileinto" on it.
Example:
require "fileinto";
require "mailboxid";
if header :contains ["from"] "coyote" {
if mailboxidexists "F6352ae03-b7f5-463c-896f-d8b48ee3" {
fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3";
} else {
fileinto "INBOX.harassment";
}
}
6. Formal Syntax
test /= ":mailboxidexists" string-list
tag /= ":mailboxid"
7. Security considerations
This document does not add any security considerations beyond those
in [RFC5228], [RFC5490] and [I-D.ietf-extra-imap-objectid].
Implementers are referred to the security considerations sections of
those documents.
8. IANA considerations
IANA are requested to add a capability to the sieve-extensions
registry:
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To: iana@iana.org
Subject: Registration of new Sieve extension
Capability name: mailboxid
Description: adds test for checking for mailbox existence by objectid
and a new optional argument to fileinto to select the
destination mailbox using objectid.
RFC number: this RFC
Contact address: The EXTRA discussion list <extra@ietf.org>
9. Acknowledgements
This document borrows heavily from [RFC5490] for the matching
mailboxexists test, and from [I-D.ietf-extra-sieve-special-use] for
an example of modifying the fileinto command.
10. TODO
Is there a more explicit way to update the grammar? It seems less
fully specified than IMAP.
11. References
11.1. Normative References
[]
Gondwana, B., "IMAP Extension for object identifiers",
draft-ietf-extra-imap-objectid-08 (work in progress),
August 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003,
<https://www.rfc-editor.org/info/rfc3501>.
[RFC5228] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
Filtering Language", RFC 5228, DOI 10.17487/RFC5228,
January 2008, <https://www.rfc-editor.org/info/rfc5228>.
[RFC5490] Melnikov, A., "The Sieve Mail-Filtering Language --
Extensions for Checking Mailbox Status and Accessing
Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March
2009, <https://www.rfc-editor.org/info/rfc5490>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References
[]
Bosch, S., "Sieve Email Filtering: Delivering to Special-
Use Mailboxes", draft-ietf-extra-sieve-special-use-02
(work in progress), March 2018.
[RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension",
RFC 4314, DOI 10.17487/RFC4314, December 2005,
<https://www.rfc-editor.org/info/rfc4314>.
Author's Address
Bron Gondwana (editor)
FastMail
Level 2, 114 William St
Melbourne VIC 3000
Australia
Email: brong@fastmailteam.com
URI: https://www.fastmail.com
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