Hopefully it contains less bugs in examples than the previous one.
Alexey
Network Working Group
Internet Draft: Sieve -- IMAP flag Extension A. Melnikov
Document: draft-melnikov-sieve-imapflags-04.txt Messaging Direct, Ltd.
Expires: April 2001 October 2000
Sieve -- IMAP flag Extension
Status of this memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are
working documents of the Internet Engineering Task Force (IETF), its
areas, and its working groups. Note that other groups may also
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Internet-Drafts are draft documents valid for a maximum of six
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The protocol discussed in this document is experimental and subject
to change. Persons planning on either implementing or using this
protocol are STRONGLY URGED to get in touch with the author before
embarking on such a project.
Copyright
Copyright (C) The Internet Society 2000. All Rights Reserved.
Abstract
Recent discussions have shown that it is desirable to set
different [IMAP] flags on message delivery. This can be done, for
example, by a SIEVE interpreter that works as a part of a Mail Delivery
Agent.
This document describes an extension to the Sieve mail filtering
language for setting [IMAP] flags. The extension allows to set both
[IMAP] system flags and [IMAP] keywords.
0. Meta-information on this draft
This information is intended to facilitate discussion. It will be
removed when this document leaves the Internet-Draft stage.
0.1. Discussion
This draft is intended to be compared with the Sieve mail filtering
language, an Internet-Draft being discussed on the MTA Filters
mailing list at <ietf-mta-filters(_at_)imc(_dot_)org>. Subscription
requests
can be sent to <ietf-mta-filters-request(_at_)imc(_dot_)org> (send an
email
message with the word "subscribe" in the body). More information on
the mailing list along with a WWW archive of back messages is
available at <http://www.imc.org/ietf-mta-filters/>.
0.2. Open issues
1. Do we want to use special actions that work with global state or use
optional tagged arguments?
Allow both? Currently the draft allows both models.
2. If we decide to keep both, what "keep"/"fileinto" without tagged
arguments means: don't set any flags
or use global flags? I would rather ignore flags completely to keep
current "keep"/"fileinto" behavior.
This breaks backward compatibility with the previous draft and if this is
a big concern it can be addressed
in the next revision of the draft.
3. Add example that describes why implicit way is useful?
4. Should the document repeat when describing flag manipulation actions that
they have no affect
if non of ":globalflags", ":globalflags_plus" or ":globalflags_minus" is
specified?
5. ":globalflags_plus" and ":globalflags_minus" names are ugly. Suggestions
are welcome.
0.3. To be done
Text will be reworked not to reference "internal variable".
0.4. Changes from the version submitted to the SIEVE mailing list
1. Added addflag and removeflag actions
2. Changed the semantics of setflag (setflag is not additive any more)
3. Corrected section "Interaction with Other Sieve Actions".
Removed incorrect reference to the forward action as to an
action that prohibits setflag.
4. Added paragraph about the mutual order of "fileinto"/"keep" and
"setflag"/"addflag"/"removeflag" actions.
0.5. Changes from the revision 00
1. Corrected Capability Identifier section (Section 2)
2. Corrected "Interaction with Other Sieve Actions" section (Section 4)
3. Examples were updated to be compatible with Sieve-07 draft
4. Added "mark" and "unmark" actions
0.6. Changes from the revision 01
1. Some language fixes based on Tony Hansen comments
2. Clarified that the extension allows to set both IMAP System Flags and
Keywords
0.7. Changes from the revision 02
1. BugFix: all backslashes must be escaped
2. Added extended example and more detailed description of
"addflag"/"removeflag" additivity.
3. Minor example bugfixes
0.8. Changes from the revision 03
1. Added second way to specify flags to be set (via optional tagged
arguments). [Tim Showalter]
2. Rules for using Reject with imapflags relaxed. [Randall Gellens]
3. Removed ABNF section completely, added syntax description to action
definition. [Tim Showalter]
4. Cleaned up the example. [Ken Murchison]
5. Added [FM] acronym (Flag Manupulation)
6. Clarified "mark"/"unmark" bahavior. [Randall Gellens}
1. Introduction
This is an extension to the Sieve language defined by [SIEVE] for
setting [IMAP] flags. There are two major ways to specify which flags should
be set: explicit, that lists flags using tagged argument for "keep" and
"fileinto" and implicit, that uses actions that work with the global state
("setflag", "addflag", "removeflag", "mark" and "unmark"). There is also
possible
to combine the advantages of both ways. The first approach is described in
section 4.
The second is described in the sections 3 and 4.
This document doesn't dictate how the SIEVE interpreter will set the [IMAP]
flags. In particular, the SIEVE interpreter may work as an IMAP client,
or may have direct access to the mailstore.
SIEVE interpreters that don't support integration with IMAP
SHOULD ignore this extension.
2. Conventions used.
Conventions for notations are as in [SIEVE] section 1.1, including
use of [KEYWORDS] and "Syntax:" label for the definition of action and
tagged arguments syntax.
Global flags are those that are set by
"setflag"/"addflag"/"removeflag"/"mark"/"unmark" actions.
"[FM]" (Flag Manipulation) acronym references any of
"setflag"/"addflag"/"removeflag"/"mark"/"unmark"
actions.
The capability string associated with extension defined in this document
is "imapflags".
3. Actions
All actions described in this specification (setflag, addflag, removeflag,
mark, unmark) operate on an internal variable that contains the set of
[IMAP] flags
associated with the message being delivered. When the interpreter starts
executing
a script this variable contains an empty set. The "addflag" action adds flags
to the existing set. The "removeflag" action removes flags from the existing
set.
The "setflag" action replaces the existing set of flags with a new set.
Whenever the interpreter encounters a "fileinto" or "keep" action it files
the message with the current set of flags.
3.1. Setflag Action
Syntax: setflag <list-of-flags: string-list>
Setflag is used for setting [IMAP] system flags or keywords. Setflag
replaces any previously set flags. It should be used together with
"keep"
or "fileinto". It MUST be ignored if mailstore or target mailbox doesn't
support the storing of any flags.
Flags can be set only for the message that is currently being processed by
SIEVE. When called with "keep", setflag sets flags in the user's main
mailbox. When called with "fileinto", setflag sets flags in the
mailbox indicated by the parameter.
The order of "setflag"/"fileinto" or "setflag"/"keep" is important in the
script. Any setflag action applies only to all subsequent "fileinto"/"keep"
actions in a script till next occurence of [FM] action.
Server MUST ignore all flags that it can't store permanently. This
means, in particular, that if the user's main mailbox can't store any
flags, then the following SIEVE script produces no actions
Example: if size :over 500K {
setflag "\\Deleted";
}
A more substantial example is:
Example:
if header :contains "from" "boss(_at_)frobnitzm(_dot_)edu" {
setflag "\\Flagged";
fileinto :globalflags "INBOX.From Boss";
}
3.2. Addflag action
Syntax: addflag <list-of-flags: string-list>
Addflag is used for setting [IMAP] flags. However unlike setflag it
doesn't replace any previously set flags. This means that multiple
occurrences of addflag are treated additively.
For example, the following two actions
addflag "\\Deleted";
addflag "\\Answered";
produce the same result as the single action
addflag ["\\Deleted", "\\Answered"];
In all other respects addflag behaves the same way as
setflag.
3.3. Removeflag Action
Syntax: removeflag <list-of-flags: string-list>
Removeflag is used for setting [IMAP] flags. Removeflag clears
flags previously set by "setflag"/"addflag". Calling removeflag with a
flag that wasn't set before is not an error and is ignored.
Multiple occurrences of removeflag are treated additively.
In all other respects removeflag behaves the same way as
setflag.
Example:
if header :contains "Disposition-Notification-To"
"mel(_at_)example(_dot_)com" {
addflag "$MDNRequired";
}
if header :contains "from" "imap(_at_)cac(_dot_)washington(_dot_)edu" {
removeflag "$MDNRequired";
fileinto :globalflags "INBOX.imap-list";
}
3.4. Mark and Unmark Actions
Syntax: mark
Syntax: unmark
The mark action allows a message to be marked as urgent. Conformant
implementation MUST
set \Flagged [IMAP] flag, but MAY also set other [IMAP] flags as well. Thus
the mark action is
semantically equivalent to 'addflag "\\Flagged"'.
The unmark action allows the flag previously set by the Mark action to be
unset.
Unmark MUST unset the [IMAP] \Flagged flag and all other flags that could be
added with mark.
Unmark MUST NOT unset any other flags. This means that the following script
does nothing:
mark;
unmark;
The unmark action is semantically equivalent to 'removeflag "\\Flagged"'.
4. Tagged arguments
This specification adds several optional tagged arguments that alter the
behavior of actions
"keep" and "fileinto". Only one of the following 4 tagged arguments can be
used with "keep" or
"fileinto". They specify that some flag or combination of flags should be
set when they deliver
the message to the target mailbox. If non of the 4 following tagged
arguments is specified,
"keep" or "fileinto" will not set any flag when they deliver the message to
the mailbox.
Syntax: ":globalflags_plus" <list-of-flags: string-list>
The copy of the message filed into mailbox will have both global flags and
flags listed after
":globalflags_plus".
Syntax: ":globalflags_minus" <list-of-flags: string-list>
The copy of the message filed into mailbox will have all global flag with
exception of flags
listed after ":globalflags_minus".
Syntax: ":globalflags"
The copy of the message filed into mailbox will have only global flags.
Syntax: ":flags" <list-of-flags: string-list>
The copy of the message filed into mailbox will have only flags listed after
":flags".
Global flags set by any of [FM] actions are ignored.
5. Interaction with Other Sieve Actions
Sieve actions sometimes prohibit each other in order to make
filtering scripts less likely to cause serious problems.
The SIEVE interpreter MUST ignore any [FM]
actions when they are used with reject. The SIEVE interpreter MUST ignore
these
commands when no keep (implicit or explicit) or fileinto actions will be
taken.
If the script uses any of [FM] actions
together with reject a SIEVE verifier SHOULD warn the user using available
means that
the script contains actions that has no effect when used with reject.
6. Other Considerations
This extension intentionally doesn't allow setting [IMAP] flags on an
arbitrary message in the [IMAP] message store.
7. Security Considerations
Security considerations are discussed in the [IMAP] and [SIEVE].
It is belived that this extension doesn't introduce any
additional security concerns.
8. Extended example
#
# Example Sieve Filter
# Declare any optional features or extension used by the script
#
require ["fileinto", "imapflags"];
#
# Move large messages to special mailbox
#
if size :over 1M
{
addflag "$Big";
if header :is "From" "boss(_at_)company(_dot_)com"
{
# The message will be marked as "\Flagged $Big" when filed into mailbox "Big
messages"
addflag "\\Flagged";
}
fileinto :globalflags "Big messages";
}
if header :is "From" "grandma(_at_)example(_dot_)net"
{
addflag ["\\Answered", "$MDNSent"];
# If the message is bigger than 1Mb it will be marked as "$Big \Answered
$MDNSent"
# when filed into mailbox "grandma". If the message is shorter than 1Mb it
will be marked as
# "\Answered $MDNSent"
fileinto :globalflags "GrandMa"; # move to "GrandMa" folder
}
#
# Handle messages from known mailing lists
# Move messages from IETF filter discussion list to filter folder
#
if header :is "Sender" "owner-ietf-mta-filters(_at_)imc(_dot_)org"
{
setflag "\\Flagged";
# Message will always have just "\Flagged" flag
keep :globalflags;
}
#
# Keep all messages to or from people in my company
#
elsif anyof address :domain :is ["From", "To"] "company.com"
{
keep :globalflags; # keep in "In" folder
}
#
# Try and catch unsolicited email. If a message is not to me,
# or it contains a subject known to be spam, file it away.
#
elsif anyof (not address :all :contains
["To", "Cc", "Bcc"] "me(_at_)company(_dot_)com",
header :matches "subject"
["*make*money*fast*", "*university*dipl*mas*"])
{
removeflag "\\Flagged";
# If message header does not contain my address,
# it's from a list.
fileinto :globalflags "spam"; # move to "spam" folder
}
else
{
# Move all other (non-company) mail to "personal"
# folder.
fileinto :globalflags "personal";
}
9. Acknowledgments
This document has been revised in part based on comments and
discussions which took place on and off the SIEVE mailing list.
The help of those who took the time to review the draft and make
suggestions is appreciated, especially that of Tim Showalter,
Barry Leiba, Randall Gellens, Ken Murchison and Cyrus Daboo.
Special thanks to Tony Hansen, David Lamb and Roman Migal for helping
me explain better the concept.
10. Author's Address
Alexey Melnikov
Messaging Direct, Ltd.
Address : #900, 10117 Jasper Avenue, Edmonton, Alberta, Canada,
T5J1W8
Email: mel(_at_)messagingdirect(_dot_)com
Appendices
Appendix A. References
[SIEVE] Showalter, T., "Sieve: A Mail Filtering Language", Mirapoint,
Work in Progress, draft-showalter-sieve-XX.txt
[ABNF] Crocker, D., "Augmented BNF for Syntax Specifications: ABNF",
Internet Mail Consortium, RFC 2234, November, 1997.
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", Harvard University, RFC 2119, March 1997.
[IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1",
University of Washington, RFC 2060, December 1996.
Appendix B. Full Copyright Statement
Copyright (C) The Internet Society 2000. All Rights Reserved.
This document and translations of it may be copied and furnished to
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or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.