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 distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). 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 . Subscription requests can be sent to (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 . 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 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@frobnitzm.edu" { setflag "\\Flagged"; fileinto :globalflags "INBOX.From Boss"; } 3.2. Addflag action Syntax: addflag 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 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@example.com" { addflag "$MDNRequired"; } if header :contains "from" "imap@cac.washington.edu" { removeflag "$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" The copy of the message filed into mailbox will have both global flags and flags listed after ":globalflags_plus". Syntax: ":globalflags_minus" 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" 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@company.com" { # The message will be marked as "\Flagged $Big" when filed into mailbox "Big messages" addflag "\\Flagged"; } fileinto :globalflags "Big messages"; } if header :is "From" "grandma@example.net" { addflag ["\\Answered", "$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@imc.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@company.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@messagingdirect.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. 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