Internet Draft: Common IMAP keywords A. Melnikov Document: draft-melnikov-imap-keywords-03.txt Isode Ltd. Expires: February 2006 August 2005 Intended category: Informational Common IMAP keywords Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. A revised version of this draft document will be submitted to the RFC editor as an Informational document. Discussion and suggestions for improvement are requested, and should be sent to the IMAP4 Mailing list (imap@CAC.Washington.EDU) <>. To subscribe to the list, send email to with the text "subscribe imap YourName" in the body of the message. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2005). Abstract The aim of this document is to document some common [IMAP4] keywords for the purpose of improving interoperability between different IMAP mail clients. The document both documents some keywords already in use, as well as introduces several new ones. Melnikov Expires: February 2006 [Page 1] INTERNET DRAFT Common IMAP keywords August 2005 This document also establishes a new IANA registry for IMAP keywords and defines a procedure for keyword registration. Table of Contents Abstract .................................................... 2 0. To do ....................................................... 1 1. Conventions Used in this Document ........................... 2 2. IMAP keyword registrations .................................. 3 2.1 $Forwarded .................................................. 3 2.2 Keywords related to junk filtering .......................... X 2.3 $Work ....................................................... X 2.4 $Personal ................................................... X 2.5 $ShouldReply ................................................ X 2.6 $ToDo ....................................................... X 2.7 $Important .................................................. X 3. Security Considerations ..................................... X 4. Known issues with mail clients .............................. X 5. Formal Syntax ............................................... X 6. IANA Considerations ......................................... X 7. Acknowledgments ............................................. X 8. Normative References ........................................ X 9. Author's Addresses .......................................... X 10. Intellectual Property ....................................... X 11. Full Copyright Statement .................................... X 1. Conventions Used in this Document "C:" and "S:" in examples show lines sent by the client and server respectively. The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in this document when typed in uppercase are to be interpreted as defined in "Key words for use in RFCs to Indicate Requirement Levels" [KEYWORDS]. <> Melnikov Expires: February 2006 [Page 2] INTERNET DRAFT Common IMAP keywords August 2005 2. IMAP keyword registrations 2.1 $Forwarded Purpose: $Forwarded is used by several IMAP clients to specify that the message was resent to another email address, embedded within or attached to a new message. This keyword is set by the mail client when it successfully forwards the message to another email address. Typical usage of this keyword is to show a different (or additional) icon for a message that has been forwarded. Private or Shared on a server: either Is it an advisory keyword or may it cause an automatic action: advisory When/by whom the keyword is set/cleared: This keyword can be set either by a delivery agent or a mail client. Once set the flag SHOULD NOT be cleared. Notes: There is no way to tell if a message with $Forwarded keyword set was forwarded more than once. Corresponding ANNOTATE attribute: "/message/flags/$forwarded" (default mapping as described in ANNOTATE) Additional IMAP capabilities: none. Security Considerations: A server implementing this keyword as a shared keyword, may disclose that a confidential message was forwarded. 2.2 Keywords related to junk filtering This section defines two groups of keywords related to mail filtering. 2.2.1 $AutoJunk/$AutoNotJunk/$AutoMaybeJunk Purpose: An automated system (delivery agent, mail filtering software or IMAP4/POP3 server) may mark a message with one of the following keywords: $AutoJunk - a message is most likely to contain junk; $AutoNotJunk - a message is most likely not to contain junk; $AutoMaybeJunk - a message may contain junk; $AutoMaybeJunk, for example, may be used by a Bayesian filtering Melnikov Expires: February 2006 [Page 3] INTERNET DRAFT Common IMAP keywords August 2005 software that can't classify a message with certainty as being either junk or not junk. These keyword can be used to mark, group or hide ($AutoJunk) offensive messages. However no automatic irreversible action (in particular message deletion, bouncing, moving into a different mailbox) should be allowed on messages marked as $AutoJunk. Private or Shared on a server: may be shared. SHOULD be shared when automatically set by a delivery agent or an IMAP4/POP3 server. Is it an advisory keyword or may it cause an automatic action: advisory When/by whom the keyword is set/cleared: Any one of the described keywords can be set automaticall either by a delivery agent, a mail filtering software or a mail (IMAP4/POP3) server. Once set, the value SHOULD NOT be changed. If $AutoJunk and/or $AutoMaybeJunk are used to hide all messages with those flags from the current view, the mail client MUST implement a mode of operation when it is possible to see the hidden messages. Notes: $AutoJunk, $AutoNotJunk and $AutoMaybeJunk are mutually exclusive. If more than one of them is set for a message, the mail client MUST treat this as if none of them is set and SHOULD remove all of them from the IMAP server. Notes: See also section 3.2.2 that talks how $AutoJunk, $AutoNotJunk and $AutoMaybeJunk may interact with $Junk and $NotJunk. Corresponding ANNOTATE attribute: "/message/flags/$autojunk" "/message/flags/$autonotjunk" "/message/flags/$automaybejunk" (default mapping as described in ANNOTATE) Additional IMAP capabilities: none. Security Considerations: A message marked with $AutoJunk keyword by an automated system might not be considered junk by any or even all users of the system. Thus, any automated actions are prohibited based on the keywords described in this section. 2.2.2 $Junk/$NotJunk Purpose: The user (or a delivery agent on behalf of the user) may choose to mark a message as either definitely containing junk ($Junk) or definitely not containing junk ($NotJunk). This keyword can be Melnikov Expires: February 2006 [Page 4] INTERNET DRAFT Common IMAP keywords August 2005 used to mark (and potentially move/delete messages later), group or hide offensive messages. If none of $Junk or $NotJunk is present for a messages, a mail client MAY treat $AutoJunk (section 3.2.1) as $Junk and $AutoNotJunk (section 3.2.1) as $NotJunk. However, in this case no automatic irreversible action MUST be done on the message. <> Private or Shared on a server: private Is it an advisory keyword or may it cause an automatic action: advisory When/by whom the keyword is set/cleared: $Junk/$NotJunk can be set either by a delivery agent or a mail client on users behalf. The user must be able to change $Junk to $NotJunk or vice versa at any time. If the mail client hides all messages with $Junk keyword from the current view, the mail client MUST implement a mode when it is possible to see all messages marked as $Junk. Notes: 1). $Junk and $NotJunk are mutually exclusive. If more than one of them is set for a message, the mail client MUST treat this as if none of them is set and SHOULD remove both of them from the IMAP server. 2). $Junk is also mutually exclusive with $Work and $Personal. If more than one of them is set for a message, the mail client MUST treat this as if none of them is set and SHOULD remove all of them from the IMAP server. 3). The combination of $NotJunk and $AutoJunk keywords indicates that the automated system made a false-positive. The combination of $Junk and $AutoNotJunk keywords indicates that the automated system made a false-negative. Both combinations can be used to train the automated system that set $AutoJunk/$AutoNotJunk to do a better job in classifying junk versa not junk. 4). <> Corresponding ANNOTATE attribute: "/message/flags/$junk" "/message/flags/$notjunk" (default mapping as described in ANNOTATE) Additional IMAP capabilities: none. Security Considerations: A message marked with $Junk keyword by one user might not be considered junk by another (or even by the same user under different circumstances), so no automatic action can be initiated when this flag is set. 2.3 $Work Purpose: The user (or a delivery agent on behalf of the user) may choose to mark a message as related to work. This keyword can be used to automatically move a message to a different mailbox or to group messages. Private or Shared on a server: private Is it an advisory keyword or may it cause an automatic action: advisory When/by whom the keyword is set/cleared: This keyword can be set either by a delivery agent or a mail client on users behalf. The user must be able to set and unset this keyword. Notes: This keyword is mutually exclusive with $Junk and $Personal. If more than one of the $Junk, $Work or $Personal keywords is set for a message, the mail client MUST treat this as if none of them is set and SHOULD remove all of them from the IMAP server. Note: $Work and $Personal can be used to help implement a "poor man" multiple personalities (actually just two personalities) feature in a mail client. Corresponding ANNOTATE attribute: "/message/flags/$work" (default mapping as described in ANNOTATE) Additional IMAP capabilities: none. Security Considerations: <>. 2.4 $Personal Melnikov Expires: February 2006 [Page 6] INTERNET DRAFT Common IMAP keywords August 2005 Purpose: The user (or a delivery agent on behalf of the user) may choose to mark a message as personal. This keyword can be used to automatically move a message to a different mailbox or to group messages. Private or Shared on a server: private Is it an advisory keyword or may it cause an automatic action: advisory When/by whom the keyword is set/cleared: This keyword can be set either by a delivery agent or a mail client on users behalf. The user must be able to set and unset this keyword. Notes: This keyword is mutually exclusive with $Junk and $Work. If more than one of the $Junk, $Work or $Personal keywords is set for a message, the mail client MUST treat this as if none of them is set and SHOULD remove all of them from the IMAP server. Note: $Work and $Personal can be used to help implement a "poor man" multiple personalities (actually just two personalities) feature in a mail client. Corresponding ANNOTATE attribute: "/message/flags/$personal" (default mapping as described in ANNOTATE) Additional IMAP capabilities: none. Security Considerations: <>. 2.5 $ShouldReply Purpose: The user may mark a message with this keyword to specify that the message requires a reply. One possible use of this keyword is to group in some way all messages having this keyword. Another possible use would be to periodically remind the user to send replies to messages marked with this keyword. When a reply to this message is sent, the mail client MUST remove this keyword and MUST set the \Answered flag. <> Private or Shared on a server: private Is it an advisory keyword or may it cause an automatic action: advisory(<>) Melnikov Expires: February 2006 [Page 7] INTERNET DRAFT Common IMAP keywords August 2005 When/by whom the keyword is set/cleared: This keyword can be set either by a delivery agent or a mail client on users behalf (for example, "should reply to all messages from boss with particular subject"). The user must be able to set and unset this keyword. Notes: <>. Corresponding ANNOTATE attribute: "/message/flags/$shouldreply" (default mapping as described in ANNOTATE) Additional IMAP capabilities: none. Security Considerations: <> 2.6 $ToDo Purpose: The user may mark a message with this keyword to specify that the message requires some kind of action from the user, for example phone call, or reply (in the latter case the $ShouldReply keyword would also be set). One possible use of this keyword is to group in some way all messages having this keyword. Private or Shared on a server: private Is it an advisory keyword or may it cause an automatic action: advisory(<>) When/by whom the keyword is set/cleared: This keyword can be set either by a delivery agent or a mail client on users behalf. The user must be able to set and unset this keyword. Notes: <>. Corresponding ANNOTATE attribute: "/message/flags/$todo" (default mapping as described in ANNOTATE) Additional IMAP capabilities: none. Security Considerations: <> 2.7 $Important Purpose: <<[IMAP4] doesn't specify exact semantics of the \Flagged flag. It suggests that it is up to a MUA to assign any special meaning to it. Most intuitive meaning of \Flagged is probably to mark Melnikov Expires: February 2006 [Page 8] INTERNET DRAFT Common IMAP keywords August 2005 that message as important. However since the same user can use multiple MUAs from different vendors, there are some MUAs that use it for different purposes. In order to introduce a consistent "Important" mark a new flag is required. This document defines a new keyword $Important for this purpose.>> Private or Shared on a server: private Is it an advisory keyword or may it cause an automatic action: advisory When/by whom the keyword is set/cleared: This keyword can be set either by a delivery agent or a mail client on users behalf, for example if the message includes header field "Importance" with the value "High". The user must be able to set and unset this keyword. Notes: ... <> <> Corresponding ANNOTATE attribute: ... Additional IMAP capabilities: ?. Security Considerations: ... 3. Security Considerations << Danger of an automatic initiation of an action based on $Junk keyword >> 4. Known issues with mail clients A popular open source mail client Mozilla implemented "labels". Each label has associated color and name (description) that can be changed by a user, a label name can be stored on an IMAP server as a keyword. Mozilla uses 5 hardcoded keywords $Label1, $Label2, $Label3, $Label4 and $Label5. However, there is a problem with how Mozilla implemented this feature. Each label has a fixed IMAP keyword and a description that can be changed. Now imagine that two users (or even the same user on two different computers) configured Mozilla Melnikov Expires: February 2006 [Page 9] INTERNET DRAFT Common IMAP keywords August 2005 differently so that the label $Label1 has description "Important" on one machine and description "Junk" on another. As label description is not stored on the IMAP server there is an interoperability problem. There are two possible ways to fix the problem. One way is to disallow editing of label descriptions (the defaults are Important/Work/Personal/ToDo/Later) and to use matching keywords from this document (or create new ones if necessary). Another way is to allow users to edit keyword names in addition to label descriptions. This is a feature for advanced users and should have a detailed documentation describing how to correctly select keyword names. 5. Formal Syntax Formal syntax is defined using ABNF [ABNF], extending the ABNF rules in section 9 of [IMAP4]. Elements not defined here can be found in the [ABNF] and [IMAP4]. Except as noted otherwise, all alphabetic characters are case- insensitive. The use of upper or lower case characters to define token strings is for editorial clarity only. Implementations MUST accept these strings in a case-insensitive fashion. flag_keyword ::= spe_keywords / other_keywords spe_keywords ::= "$" ( "Forwarded" / "Important" / "ShouldReply" / / "Work" / "Personal" ) / junk_keywords junk_keywords ::= (junkauto_keys / junkmanual_keys) junkauto_keys ::= "AutoJunk" / "AutoNotJunk" / "AutoMaybeJunk" junkmanual_keys ::= "Junk" / "NotJunk" other_keywords ::= atom 6. IANA Considerations 6.1. IMAP Keyword Registry IANA is requested to establish a new registry for IMAP keywords. Melnikov Expires: February 2006 [Page 10] INTERNET DRAFT Common IMAP keywords August 2005 Registration of an IMAP keyword is requested by filling in the following template: Subject: Registration of IMAP keyword X IMAP keyword name: Purpose (description): Private or Shared on a server: (One of PRIVATE, SHARED or BOTH) Is it an advisory keyword or may it cause an automatic action: When/by whom the keyword is set/cleared: Related keywords: (for example "mutually exclusive with keywords Y and Z") Additional IMAP capabilities: Security considerations: Published specification (recommended): Person & email address to contact for further information: Intended usage: (One of COMMON, LIMITED USE or OBSOLETE) Owner/Change controller: Note: (Any other information that the author deems interesting may be added here, for example if the keyword(s) is supported by existing clients.) and sending it via electronic mail to . Registration of IMAP keywords intended for common use requires expert review. This can be performed by posting a review request to IMAP mailing list <<>>. IMAP keywords intended for widespread use should be standardized through the normal IETF process, when appropriate. Registration of vendor specific keywords is done on First Come First Serve basis and doesn't require an expert review. However such review is still encouraged. <> Melnikov Expires: February 2006 [Page 11] INTERNET DRAFT Common IMAP keywords August 2005 6.1.1. Comments on IMAP Keywords' Registrations Comments on registered IMAP Keywords should first be sent to the "owner" of the mechanism and/or to the IMAP mailing list.<<>> Submitters of comments may, after a reasonable attempt to contact the owner and after soliciting comments on the IMAP mailing list, request IANA to attach their comment to the IMAP keyword registration itself by sending mail to . At IANA sole discretion, IANA may attach the comment to the IMAP keyword registration. 6.1.2. Change Control Once an IMAP keyword registration has been published by IANA, the author may request a change to its definition. The change request follows the same procedure as the registration request. The owner of a IMAP keyword may pass responsibility for the IMAP keyword to another person or agency by informing IANA; this can be done without discussion or review. The IESG may reassign responsibility for an IMAP keyword. The most common case of this will be to enable changes to be made to mechanisms where the author of the registration has died, moved out of contact or is otherwise unable to make changes that are important to the community. IMAP keyword registrations may not be deleted; <>. The IESG is considered to be the owner of all IMAP keywords which are on the IETF standards track. 6.2. Initial registrations <<>> 7. Acknowledgments The creation of this document was prompted by one of many discussions on the IMAP mailing list. John Neystadt co-authored the first revision of this document. Special thanks to Chris Newman, David Harris, Lyndon Nerenberg and Melnikov Expires: February 2006 [Page 12] INTERNET DRAFT Common IMAP keywords August 2005 Mark Crispin for reviewing the document. However all errors or omissions must be attributed to the author of this document. The author would also like to thank the developers of Mozilla mail clients for providing food for thoughts. 8. Normative References [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4rev1", RFC 3501, University of Washington, March 2003. [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. [RFC 2822] Resnick, P., "Internet Message Format", RFC 2822, QUALCOMM Incorporated, April 2001. [HEADERS] Palme, J., "Common Internet Message Headers", RFC 2076, Stockholm University/KTH, February 1997. [ANNOTATION] Gellens, R., Daboo, C., "IMAP ANNOTATE Extension", work in progress, 9. Author's Addresses Alexey Melnikov Isode Limited Address: 5 Castle Business Village, 36 Station Road, Hampton, Middlesex, United Kingdom, TW12 2BX Phone: +44 77 53759732 Email: alexey.melnikov@isode.com Melnikov Expires: February 2006 [Page 13] INTERNET DRAFT Common IMAP keywords August 2005 10. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. 11. Full Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Appendix A. To do list and open issues [[Note to RFC Editor: delete this section before publication.]] Melnikov Expires: February 2006 [Page 14] INTERNET DRAFT Common IMAP keywords August 2005 Open issues are enclosed in << and >> through out this document. This document is still very raw. Comments are encouraged. <> <> <> <> <> Appendix B. Change History [[Note to RFC Editor: delete this section before publication.]] Changes from draft-melnikov-imap-keywords-01 1. Dropped $Adult as it was too controversial. 2. Replaced $Spam with $Junk/$NotJunk/$AutoJunk/$AutoNotJunk and $AutoMaybeJunk. Reworked text to reflect this and tried to catch all different interactions between newly introduced keywords. 3. Added more usage examples for different keywords. 4. Updated IMAP4rev1 reference. 5. Added description of a problem with labels in Mozilla. Changes from draft-melnikov-imap-keywords-02 1. Added $ToDo. 2. Cleaned up some open issues, in particular removed text prescribing which RFC 2822 header fields should cause autosetting of $Important. 3. Added IANA considerations section and registration procedure. 4. Fixed ABNF - extra leading $ was used for some keywords. Melnikov Expires: February 2006 [Page 15]