Sieve Email Filtering: Delivering to Special-Use Mailboxes
RFC 8579
Internet Engineering Task Force (IETF) S. Bosch
Request for Comments: 8579 Open Xchange Oy
Category: Standards Track May 2019
ISSN: 2070-1721
Sieve Email Filtering: Delivering to Special-Use Mailboxes
Abstract
The SPECIAL-USE capability of the IMAP protocol (RFC 6154) allows
clients to identify special-use mailboxes, e.g., where draft or sent
messages should be put. This simplifies client configuration. 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 test for checking whether a special-use attribute
is assigned for a particular mailbox or any mailbox, and it adds the
ability to file messages into a mailbox identified solely by a
special-use attribute.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8579.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Bosch Standards Track [Page 1]
RFC 8579 Sieve: Special-Use Mailboxes May 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Test "specialuse_exists" . . . . . . . . . . . . . . . . . . 3
3.1. Equivalent IMAP Operations . . . . . . . . . . . . . . . 4
4. ":specialuse" Argument to "fileinto" Command . . . . . . . . 5
4.1. Mailboxes Created Implicitly by the "fileinto" Command . 6
4.2. Equivalent IMAP Operations . . . . . . . . . . . . . . . 7
5. Sieve Capability Strings . . . . . . . . . . . . . . . . . . 8
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 11
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Commonly, several mailboxes in an IMAP message store [IMAP] have a
special use. For example, there can be a special-use mailbox for
storing the user's draft messages, for keeping copies of sent
messages, and for collecting spam messages that were classified as
such at delivery. The SPECIAL-USE capability [SPECIAL-USE] of the
IMAP protocol defines mailbox attributes that identify these special
mailboxes explicitly to the client. This way, client configuration
is simplified significantly. Using the CREATE-SPECIAL-USE capability
[SPECIAL-USE], IMAP clients can also configure these attributes
dynamically based on user preference.
Unlike the IMAP protocol, the Sieve mail filtering language [SIEVE]
currently cannot freely access these special-use mailbox attributes.
Particularly, the Sieve interpreter has no means to identify a
mailbox with a particular special-use attribute. This would be very
useful, for example, to find the user's "Spam" mailbox at delivery.
In Sieve, limited access to the special-use attributes is provided
using the "mboxmetadata" extension [SIEVE-MAILBOX], which allows
testing for the presence of a special-use attribute in the "/private/
specialuse" IMAP METADATA [IMAP-METADATA] entry of a mailbox. Still,
not all implementers will be willing to add the complexity of the
IMAP METADATA capability just to provide access to special-use
attributes to the Sieve interpreter.
Show full document text