SIEVE Email Filtering Working T. Showalter
Group ??
Internet-Draft N. Freed, Ed.
Expires: March 25, 2006 Sun Microsystems
September 21, 2005
Sieve Email Filtering: Vacation Extension
draft-ietf-sieve-vacation-03
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.
This Internet-Draft will expire on March 25, 2006.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document describes an extension to the Sieve email filtering
language for an autoresponder similar to that of the Unix "vacation"
command for replying to messages. Various safety features are
included to prevent problems such as message loops.
Change History (to be removed prior to publication as an RFC)
Showalter & Freed Expires March 25, 2006 [Page 1]
Internet-Draft Sieve Vacation Extension September 2005
Changes from draft-showalter-sieve-vacation-06.txt:
1. Updated to XML source.
2. Added :from parameter.
3. Added :handle parameter.
4. Added more detailed description of :subject parameter
5. Clarified some discussion text.
6. Fixed various minor typos.
7. Refinement of duplicate response suppression semantics
8. Added a statement that vacation is incompatible with reject
9. Prohibited the use of 8bit material in MIME headers specified
when :mime is in effect.
10. Use "Auto:" instead of "Re:" in automatically generated subject
lines
11. Added an explicit list of registered "List-*" header fields to
check for
12. Switched Syntax: label to Usage:
13. Updated draft to refer to RFC 3028bis instead of RFC 3028.
14. Removed reference to section 2.4.2.4 of RFC 3028 since the
section no longer exists in the revised version.
15. Updated reference for sieve reject, added text about refuse.
Showalter & Freed Expires March 25, 2006 [Page 2]
Internet-Draft Sieve Vacation Extension September 2005
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Capability Identifier . . . . . . . . . . . . . . . . . . . . 4
4. Vacation Action . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Days Parameter . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Previous Response Tracking . . . . . . . . . . . . . . . . 5
4.3. Subject and from parameters . . . . . . . . . . . . . . . 7
4.4. MIME Parameter . . . . . . . . . . . . . . . . . . . . . . 7
4.5. Address Parameter and Limiting Replies to Personal
Messages . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.6. Restricting Replies to Automated Processes and Mailing
Lists . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.7. Interaction with Other Sieve Actions . . . . . . . . . . . 8
4.8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Response Message Generation . . . . . . . . . . . . . . . . . 9
5.1. SMTP MAIL FROM address . . . . . . . . . . . . . . . . . . 9
5.2. Date . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.3. Subject . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.4. From . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.5. To . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.6. Auto-submitted . . . . . . . . . . . . . . . . . . . . . . 10
5.7. Message Body . . . . . . . . . . . . . . . . . . . . . . . 10
5.8. In-Reply-To and References . . . . . . . . . . . . . . . . 10
6. Relationship to Recommendations for Automatic Responses to
Electronic Mail . . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 12
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 15
Showalter & Freed Expires March 25, 2006 [Page 3]
Internet-Draft Sieve Vacation Extension September 2005
1. Introduction
This document defines an extension to the Sieve language defined in
[I-D.ietf-sieve-3028bis] for notification that messages to a
particular recipient will not be answered immediately.
2. Conventions used in this document
Conventions for notations are as in [I-D.ietf-sieve-3028bis] 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 [RFC2119].
3. Capability Identifier
Sieve implementations that implement vacation have an identifier of
"vacation" for use with the capability mechanism.
4. Vacation Action
Usage: vacation [":days" number] [":subject" string]
[":from" string] [":addresses" string-list]
[":mime"] [":handle" string] <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.
4.1. 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 as long as the minimum is greater
than 0. Sites MAY also define a maximum days value, which MUST be
greater than 7, and SHOULD be greater than 30.
Showalter & Freed Expires March 25, 2006 [Page 4]
Internet-Draft Sieve Vacation Extension September 2005
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.
If ":days" exceeds the site-defined maximum, the site-defined maximum
is used instead.
4.2. 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 the given 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.)
Tracking is not just per address, but must also take the vacation
response itself into account. A script writer might, for example,
have a vacation action that will send a general notice only once in
any two-week period. However, even if a sender has received this
general notice, it may be important to send a specific notice when a
message about something timely or something specific has been
detected.
A particular vacation response can be identified in one of two ways.
The first way is via an explicit :handle argument, which attaches a
name to the response. All vacation statements that use the same
handle will be considered to be the same response for tracking
purposes.
The second way is via a synthesis of the :subject, :from, :mime, and
reason vacation command arguments. All vacation actions that do not
contain an explicit handle and which use an identical combination of
these arguments are considered to be the same for tracking purposes.
For instance, If coyote@desert.example.org sends mail to
roadrunner@acme.example.com twice, once with the subject "Cyrus bug"
and once with the subject "come over for dinner", and
roadrunner@acme.example.com has the script shown below,
coyote@desert.example.org would receive two responses, once with the
first message, once with the second.
Showalter & Freed Expires March 25, 2006 [Page 5]
Internet-Draft Sieve Vacation Extension September 2005
require "vacation";
if header :contains "subject" "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 vacation
responses have been triggered. This behavior is REQUIRED.
There is one important exception to this rule, however. If the sieve
variables extension [I-D.ietf-sieve-variables] is used, the arguments
MUST NOT have undergone variable expansion prior to their use in
response tracking. This is so that examples like the following
script will only generate a single response to each incoming message
with a different subject line.
require ["vacation", "variables"];
if header :matches "subject" "*" {
vacation :subject "Automatic response to: ${1}"
"I'm away -- send mail to foo in my absence";
}
As noted above, the optional ":handle" parameter can be used to tell
the Sieve interpreter to treat two vacation actions with different
arguments as the same command for purposes of response tracking. The
argument to ":handle" is a string that identifies the type of
response being sent. For instance, if tweety@cage.example.org sends
mail to spike@doghouse.example.com twice, one with the subject
"lunch?" and once with the subject "dinner?", and
spike@doghouse.example.com has the script shown below,
tweety@cage.example.org will only receive a single response. (Which
response is sent depends on the order in which the messages are
processed.)
require "vacation";
if header :contains "subject" "lunch" {
vacation :handle "ran-away" "I'm out and can't meet for lunch";
} else {
vacation :handle "ran-away" "I'm out";
}
NOTE: One way to implement the necessary mechanism here is to store a
hash of either the current handle and the recipient address or, if no
handle is provided, a hash of the vacation action parameters
specifying the message content and the recipient address. If a
script is changed, implementations MAY reset the records of who has
Showalter & Freed Expires March 25, 2006 [Page 6]
Internet-Draft Sieve Vacation Extension September 2005
been responded to and when they have been responded to.
Implementations are free to limit the number of remembered responses,
provided the limit is no less than 1000. When limiting the number of
tracked responses, implementations SHOULD discard the oldest ones
first.
4.3. Subject and from parameters
The ":subject" parameter specifies a subject line to attach to any
vacation response that is generated. UTF-8 characters can be used in
the string argument; implementations MUST convert the string to
[RFC2047] encoded words if and only if non-ASCII characters are
present. Implementations MUST generate an appropriate default
subject line as specified below if no :subject parameter is
specified.
A ":from" parameter may be used to specify an alternate address to
use in the From field of vacation messages. The string must specify
a valid [RFC2822] mailbox-list. Implementations SHOULD check the
syntax and generate an error when a syntactically invalid ":from"
parameter is specified. Implementations MAY also impose restrictions
on what addresses can specified in a ":from" parameter; it is
suggested that values which fail such a security check simply be
ignored rather than causing the vacation action to fail.
4.4. MIME Parameter
The ":mime" parameter, if supplied, specifies that the reason string
is, in fact, a MIME entity as defined in [RFC2045] section 2.4,
including both MIME headers and content.
If the optional :mime parameter is not supplied, the reason string is
considered to be a UTF-8 string.
4.5. Address Parameter and Limiting Replies to Personal Messages
"Vacation" MUST NOT respond to a message unless the recipient user's
email address is in a "To", "Cc", "Bcc", "Resent-To", "Resent-Cc", or
"Resent-Bcc" line of the original message. An email address is
considered to belong to the recipient if it is one of:
1. An email address known by the implementation to be associated
with the recipient,
2. the final envelope recipient address if it's available to the
implementation, or
Showalter & Freed Expires March 25, 2006 [Page 7]
Internet-Draft Sieve Vacation Extension September 2005
3. an address specified by the script writer via the ":addresses"
argument described in the next paragraph.
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 to
belong to the recipient user in addition to the addresses known to
the implementation.
4.6. 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 [RFC2142], 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 respond to any message that contains a
"List-Id" [RFC2919], "List-Help", "List-Subscribe", "List-
Unsubscribe", "List-Post", "List-Owner" or "List-Archive" [RFC2369]
header field.
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 [RFC3834].
4.7. Interaction with Other Sieve Actions
Vacation does not affect Sieve's implicit keep action.
Vacation can only be executed once per script. A script will fail if
it attempts to execute two or more vacation actions.
Implementations MUST NOT consider vacation used with discard, keep,
fileinto, or redirect an error. The vacation action is incompatible
with the sieve reject and refuse actions [I-D.ietf-sieve-refuse-
reject].
Showalter & Freed Expires March 25, 2006 [Page 8]
Internet-Draft Sieve Vacation Extension September 2005
4.8. Examples
Here is a simple use of vacation.
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.
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.";
}
5. 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. When :mime is used the reason argument also contains
MIME header information. The headers must conform to MIME
conventions; in particular, 8bit text is not allowed.
Implementations SHOULD reject vacation :mime actions containing 8bit
header material.
5.1. 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 the NOTARY SMTP extension [RFC3461]is available.
5.2. Date
The Date field SHOULD be set to the date and time when the vacation
response was generated. Note that this may not be the same as the
time the message was delivered to the user.
Showalter & Freed Expires March 25, 2006 [Page 9]
Internet-Draft Sieve Vacation Extension September 2005
5.3. Subject
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
"Auto: " followed by the original subject.
5.4. From
Unless explicitly overridden with a :from parameter, the From field
SHOULD be set to the address of the owner of the Sieve script.
5.5. To
The To field SHOULD be set to the address of the recipient of the
response.
5.6. Auto-submitted
An Auto-Submitted field with a value of "auto-replied" SHOULD be
included in the message header of any vacation message sent.
5.7. Message Body
The body of the message is taken from the reason string in the
vacation command.
5.8. 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 SHOULD 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 be changed.
6. Relationship to Recommendations for Automatic Responses to
Electronic Mail
The vacation extension implements a "Personal Responder" in the
terminology defined in [RFC3834]. Care has been taken in this
specification to comply with the recommendations [RFC3834] makes in
regards to how personal responders should behave.
7. Security Considerations
Showalter & Freed Expires March 25, 2006 [Page 10]
Internet-Draft Sieve Vacation Extension September 2005
It is critical that implementations correctly implement the behavior
and restrictions described throughout this document. 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 unless the script changes.
If mail is forwarded from a site that uses subaddressing, it may be
impossible to list all recipient addresses with ":addresses".
Security issues associated with mail auto-responders are fully
discussed in the security consideration section of [RFC3834]. This
document is believed not to introduce any additional security
considerations in this general area.
8. 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:
Ned Freed
E-Mail: ned.freed@mrochek.com
This information should be added to the list of Sieve extensions
given on http://www.iana.org/assignments/sieve-extensions.
9. References
9.1. Normative References
[I-D.ietf-sieve-3028bis]
Guenther, P. and T. Showalter, "Sieve: An Email Filtering
Language", draft-ietf-sieve-3028bis-04 (work in progress),
July 2005, <http://www.ietf.org/internet-drafts/
draft-ietf-sieve-3028bis-04.txt>.
[I-D.ietf-sieve-variables]
Homme, K., "Sieve Mail Filtering Language: Variables
Showalter & Freed Expires March 25, 2006 [Page 11]
Internet-Draft Sieve Vacation Extension September 2005
Extension", draft-ietf-sieve-variables-04 (work in
progress), July 2005, <http://www.ietf.org/
internet-drafts/draft-ietf-sieve-variables-04.txt>.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001.
[RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service
Extension for Delivery Status Notifications (DSNs)",
RFC 3461, January 2003.
[RFC3834] Moore, K., "Recommendations for Automatic Responses to
Electronic Mail", RFC 3834, August 2004.
9.2. Informative References
[I-D.ietf-sieve-refuse-reject]
Elvey, M. and A. Melnikov, "The SIEVE mail filtering
language - reject and refuse extensions",
draft-ietf-sieve-refuse-reject (work in progress),
May 2005, <http://www.ietf.org/internet-drafts/
draft-ietf-sieve-refuse-reject.txt>.
[RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND
FUNCTIONS", RFC 2142, May 1997.
[RFC2369] Neufeld, G. and J. Baer, "The Use of URLs as Meta-Syntax
for Core Mail List Commands and their Transport through
Message Header Fields", RFC 2369, July 1998.
[RFC2919] Chandhok, R. and G. Wenger, "List-Id: A Structured Field
and Namespace for the Identification of Mailing Lists",
RFC 2919, March 2001.
Appendix A. Acknowledgements
Showalter & Freed Expires March 25, 2006 [Page 12]
Internet-Draft Sieve Vacation Extension September 2005
This extension is obviously inspired by Eric Allman's vacation
program under Unix. The authors owe a great deal to Carnegie Mellon
University, Cyrus Daboo, Lawrence Greenfield, Michael Haardt, Kjetil
Torgrim Homme, Arnt Gulbrandsen, Mark Mallet, Alexey Melnikov,
Jeffrey Hutzelman and many others whose names have been lost during
the inexcusably long gestation period of this document.
Showalter & Freed Expires March 25, 2006 [Page 13]
Internet-Draft Sieve Vacation Extension September 2005
Authors' Addresses
Tim Showalter
??
Email: tjs@psaux.com
Ned Freed (editor)
Sun Microsystems
3401 Centrelake Drive, Suite 410
Ontario, CA 92761-1205
USA
Phone: +1 909 457 4293
Email: ned.freed@mrochek.com
Showalter & Freed Expires March 25, 2006 [Page 14]
Internet-Draft Sieve Vacation Extension September 2005
Intellectual Property Statement
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.
Disclaimer of Validity
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.
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.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Showalter & Freed Expires March 25, 2006 [Page 15]
