Network Working Group T. Showalter Internet Draft: Sieve: Vacation Extension Document: draft-showalter-sieve-vacation-06.txt 26 October 2004 Expires April 25, 2004 Sieve: Vacation Extension Intellectual Property Rights Statement By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, or will be disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Status of this memo "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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html" Copyright Copyright (C) The Internet Society 2004. All Rights Reserved. Abstract This document describes an extension to the Sieve mail filtering language for an autoresponder similar to that of the Unix "vacation" command for replying to messages with certain safety features to prevent problems. Showalter Expires April 25, 2004 [Page 1]
Internet DRAFT Sieve: Vacation Extension 26 October 2004 1. Introduction This is an extension to the Sieve language defined by [SIEVE] for notification that messages will not be immediately answered. Conventions for notations are as in [SIEVE] section 1.1. The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", "CAN", and "MAY" in this document are to be interpreted as defined in [KEYWORDS]. 2. Capability Identifier Sieve implementations that implement vacation have an identifier of "vacation" for use with the capability mechanism. 3. Vacation Action Syntax: vacation [":days" number] [":addresses" string-list] [":subject" string] [":mime"] <reason: string> The "vacation" action implements a vacation autoresponder similar to the vacation command available under many versions of Unix. Its purpose is to provide correspondents with notification that the user is away for an extended period of time and that they should not expect quick responses. "Vacation" is used to respond to a message with another message. Vacation's messages are always addressed to the Return-Path address (that is, the envelope from address) of the message being responded to. 3.1. Days Parameter The ":days" argument is used to specify the period in which addresses are kept and are not responded to, and is always specified in days. The minimum value used for this parameter is normally 1. Sites MAY define a different minimum value. Sites MAY also define a maximum days value, which MUST be greater than 7, and SHOULD be greater than 30. If ":days" is omitted, the default value is either 7 or the minimum value (as defined above), whichever is greater. If the parameter given to ":days" is less than the minimum value, then the minimum value is used instead. Showalter Expires April 25, 2004 [Page 2]
Internet DRAFT Sieve: Vacation Extension 26 October 2004 If ":days" exceeds the site-defined maximum, the site-defined maximum is used instead. 3.2. Previous Response Tracking "Vacation" keeps track of all of the responses it has sent to each address in some period (as specified by the :days optional argument). If vacation has not previously sent the response to this address within that time period, it sends the "reason" argument to the SMTP MAIL FROM address of the message that is being responded to. (The SMTP MAIL FROM address should be available in the Return-path: header field if sieve processing occurs after final delivery.) Vacation responses are not just per address, but are per address per set of arguments to the vacation command. For instance, If coyote@desert.example.org sends mail to roadrunner@acme.example.com, once with the subject "Cyrus bug" and once with the subject "come over for dinner", and roadrunner@acme.example.com has the script below, coyote@desert.example.org would receive two responses, once with the first message, once with the second. Example: require "vacation"; if subject :contains "cyrus" { vacation "I'm out -- send mail to cyrus-bugs"; } else { vacation "I'm out -- call me at 304 555 1212"; } In the above example, coyote@desert.example.org gets the second message despite having gotten the first one because separate vaca- tion responses have been triggered. This behavior is REQUIRED. The "per set of arguments" described above is intended to ensure that a respondee gets all of the various possible responses, not merely the first one. So, if the :subject or :mime parameters would result in a different message, a different message MUST be sent by the implementation. If a script is changed, implementations MAY reset the records of who has been responded to and when they have been responded to. Alternatively, implementations can store records of who has received which message, perhaps by storing a hash of the message and the recipient. Implementations are free to limit the number of remembered responses, provided the limit is no less than 1000. Showalter Expires April 25, 2004 [Page 3]
Internet DRAFT Sieve: Vacation Extension 26 October 2004 Implementations SHOULD make the limit no less than 1000 per vaca- tion command if using the hash algorithm described above. When limiting the number of tracked responses, implementations SHOULD discard the oldest ones first. 3.4. MIME Parameter The ":mime" parameter, if supplied, specifies that the reason string is, in fact, a MIME part, including MIME headers (see section 2.4.2.4 of [SIEVE]). If the optional :mime parameter is not supplied, the reason string is considered to be a UTF-8 string. 3.6. Address Parameter and Limiting Replies to Personal Messages "Vacation" MUST NOT respond to a message unless the user's email address is in the "To", "Cc", "Bcc", "Resent-To", "Resent-Cc", or "Resent-Bcc" line of the original message. Implementations are assumed to know the user's email address, but users may have additional addresses beyond the control of the local mail system. Users can supply additional mail addresses that are theirs with the ":addresses" argument, which takes a string-list listing additional addresses that a user might have. These addresses are considered in addition to the addresses that the implementation knows. 3.7. Restricting Replies to Automated Processes and Mailing Lists Implementations MUST have a list of addresses that "vacation" MUST NOT send mail to. However, the contents of this list are implementation defined. The purpose of this list is to stop mail from going to addresses used by system daemons that would not care if the user is actually reading her mail. Implementations are encouraged, however, to include well-known addresses like "MAILER-DAEMON", "LISTSERV", "majordomo", and other addresses typically used only by automated systems. Additionally, addresses ending in "-request" or beginning in "owner-", i.e., reserved for mailing list software, are also suggested. Implementors may take guidance from [MAILBOXNAMES], but should be careful. Some addresses, like "POSTMASTER", are generally actually managed by people, and people do care if the user is going to be unavailable. Implementations SHOULD NOT not to respond to any message with a header that begins with "List-". Showalter Expires April 25, 2004 [Page 4]
Internet DRAFT Sieve: Vacation Extension 26 October 2004 Implementations SHOULD NOT respond to any message that has an "Auto-submitted" header field with a value other than "no". This header field is described in [AUTO]. 3.8. Interaction with Other Sieve Actions Vacation does not affect the implicit keep. Vacation can only be executed once per script. If vacation is used with another vacation, the script fails. Implementations MUST NOT consider vacation used with discard, keep, fileinto, or redirect an error. 3.9. Examples Here is a simple use of vacation. Example: require "vacation"; vacation :days 23 :addresses ["tjs@example.edu", "ts4z@landru.example.edu"] "I'm away until October 19. If it's an emergency, call 911, I guess." ; By mingling vacation with other rules, users can do something more selective. Example: require "vacation"; if header :contains "from" "boss@example.edu" { redirect "pleeb@isp.example.org"; } else { vacation "Sorry, I'm away, I'll read your message when I get around to it."; } 4. Response Message Generation This section details the requirements for the generated response message. It is worth noting that the input message and arguments may be in UTF-8, and that implementations MUST deal with UTF-8 input, although implementations MAY transcode to other character sets as regional taste dictates. Showalter Expires April 25, 2004 [Page 5]
Internet DRAFT Sieve: Vacation Extension 26 October 2004 4.1. SMTP MAIL FROM address The SMTP MAIL FROM address of the message envelope SHOULD be set to <>. NOTIFY=NEVER SHOULD also be set in the RCPT TO line during the SMTP transaction if possible. 4.2. Subject Parameter Users can specify the subject of the reply with the ":subject" parameter. If the :subject parameter is not supplied, then the subject is generated as follows: The subject is set to the characters "Re: " followed by the original subject with all leading occurrence of the characters "Re: " stripped off. 4.3. In-Reply-To and References Replies MUST have the In-Reply-To field set to the Message-ID of the original message, and the References field must be updated with the Message-ID of the original message. If the original message lacks a Message-ID, an In-Reply-To need not be generated, and References need not bne changed. 4.4. From The From field SHOULD be set to the address of the owner of the Sieve script. 4.5. To The To field SHOULD be set to the address of the recipient of the response. 4.7 Auto-submitted An Auto-Submitted field with a value of "auto-replied" SHOULD be included in the message header of any vacation message sent. 4.7. Message Body The body of the message is taken from the reason string in the vacation command. 5. Relationship to Recommendations for Automatic Responses to Electronic Mail The vacation extension implements a "Personal Responder" in the terminology defined in [AUTO]. Care has been taken in this Showalter Expires April 25, 2004 [Page 6]
Internet DRAFT Sieve: Vacation Extension 26 October 2004 specification to comply with the recommendations [AUTO] makes in regards to how personal responders should behave. 6. Security Considerations It is critical that implementations correctly implement the limitations described above. Replies MUST NOT be sent out in response to messages not sent directly to the user, and replies MUST NOT be sent out more often than the :days argument states. Security issues associated with mail auto-responders are fully discussed in the security consideration section of [AUTO]. 7. IANA Considerations The following template specifies the IANA registration of the vacation Sieve extension specified in this document: To: iana@iana.org Subject: Registration of new Sieve extension Capability name: vacation Capability keyword: vacation Capability arguments: N/A Standards Track/IESG-approved experimental RFC number: this RFC Person and email address to contact for further information: Tim Showalter E-Mail: tjs@psaux.com This information should be added to the list of sieve extensions given on http://www.iana.org/assignments/sieve-extensions. 8. Acknowledgements This extension is obviously inspired by Eric Allman's vacation program under Unix. The author owes a great deal to Carnegie Mellon University, Cyrus Daboo, Ned Freed, Lawrence Greenfield, and many others whose names have been lost during the inexcusably long gestation period of this document. 9. Author's Address Tim Showalter E-Mail: tjs@psaux.com Showalter Expires April 25, 2004 [Page 7]
Internet DRAFT Sieve: Vacation Extension 26 October 2004 Appendix A. References Appendix A.1. Normative References" [AUTO] Moore, K., "Recommendations for Automatic Responses to Electronic Mail", Internet-Draft, draft-moore-auto-email- response-05.txt. [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, Harvard University, March 1997. [MIME] Freed, N., and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, Innosoft and First Virtual, November 1996. [SIEVE] Showalter, T., "Sieve: A Mail Filtering Language", Mirapoint, Inc., RFC 3028, January, 2001. Appendix A.2. Informative References [MAILBOXNAMES] Crocker, D. "Mailbox Names for Common Services, Roles, and Functions", RFC 2142, Internet Mail Consortium, May, 1997. Appendix B. Intellectual Property Rights Statement The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 implementors or users of this specification can be obtained from the IETF Secretariat. Showalter Expires April 25, 2004 [Page 8]
Internet DRAFT Sieve: Vacation Extension 26 October 2004 Appendix C. Full Copyright Statement Copyright (C) The Internet Society 2004. 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. (See RFC 3667 sections 5.4 and 5.5.) Showalter Expires April 25, 2004 [Page 9]
