Internet Engineering Task Force (IETF)
Request for Comments: 6131
Category: Standards Track
ISSN: 2070-1721

R. George
B. Leiba
Huawei Technologies
July 2011

Sieve Vacation Extension: "Seconds" Parameter

Abstract

This document describes a further extension to the Sieve Vacation extension, allowing multiple auto-replies to the same sender in a single day by adding a ":seconds" parameter.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6131.

Copyright Notice

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
     1.1.  Terminology Used in This Document . . . . . . . . . . . . . 2
   2.  The ':seconds' Parameter  . . . . . . . . . . . . . . . . . . . 2
   3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
     5.1.  Registration of Sieve Extension . . . . . . . . . . . . . . 4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 5

1. Introduction

The Sieve [RFC5228] Vacation extension [RFC5230] defines a mechanism to generate automatic replies to incoming email messages. Through the ":days" parameter, it limits the number of auto-replies to the same sender to one per [n] days, for a specified number of days. But there are cases when one needs more granularity, if one would like to generate "vacation" replies more frequently.

This extension defines a ":seconds" parameter to provide more granularity for such situations.

1.1. Terminology Used in This Document

The upper-case key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].

2. The ':seconds' Parameter

The purpose of the ":seconds" parameter is to specify the minimum time interval (in seconds) between consecutive auto-replies to a given sender. The ":seconds" value, if specified, is used instead of the ":days" value, and works in a similar way (see the Vacation extension [RFC5230] for details). Only one of ":days" or ":seconds" is allowed -- use of both parameters in the same vacation action MUST result in a Sieve processing error.

The capability string associated with this extension is "vacation- seconds". Note that "vacation-seconds" implies "vacation", and a script with "vacation-seconds" in a "require" list can omit "vacation" from that list.

The time value is specified in seconds, and MUST be greater than or equal to 0 and less than 2**31. All valid values, from 0 to 2**31, MUST be accepted without error. Sites MAY define a minimum effective value and/or a maximum effective value. If a site chooses to do that:

Call the value specified "v(spec)".

Call the minimum effective value "v(min)".

Call the maximum effective value "v(max)".

Call the actual effective value used by the processor "v(eff)".

The following apply for determining v(eff):

If 0 <= v(spec) < v(min), then v(eff) = v(min).

If v(min) <= v(spec) <= v(max), then v(eff) = v(spec).

If v(max) < v(spec) <= 2**31, then v(eff) = v(max).

If a site imposes a maximum effective value, that value MUST be at least 86400 (one day).

If ":seconds 0" is specified and used, it means that all auto-replies are sent, and no attempt is made to suppress consecutive replies. This differs from the base vacation specification, which does not allow a time period of zero (":days 0" is forbidden); the change is necessary to allow operation of an auto-responder (see [RFC6133], and note especially example 4 in section 3 of that document).

If ":seconds" and ":days" are both omitted, a site-defined interval is used (see [RFC5230]).

   Usage: vacation [":days" number | ":seconds" number]
                   [":subject" string]
                   [":from" string]
                   [":addresses" string-list]
                   [":mime"]
                   [":handle" string]
                   <reason: string>

3. Examples

The following example will automatically reply to senders with a message that the recipient is in a meeting. Multiple replies to the same sender will only be sent every half hour (1800 seconds).

   require ["vacation-seconds"];
   vacation :addresses ["tjs@example.edu", "ts4z@landru.example.edu"]
   
            :seconds 1800
            "I am in a meeting, and do not have access to email.";

The following example is used to send an acknowledgment to every message received. A :seconds value of zero is used to reply to every message, with no removal of duplicates to the same sender. This requires that the Sieve engine allow an interval of zero; if it does not, and it imposes a minimum value, not every message will receive an auto-reply.

   require ["vacation-seconds"];
   
   vacation :handle "auto-resp" :seconds 0
       "Your request has been received.  A service
        representative will contact you as soon as
        possible, usually within one business day.";

4. Security Considerations

Security considerations for the Sieve Vacation extension [RFC5230] apply equally here. In addition, implementations SHOULD consider the number of auto-replies that might be generated by allowing small values of ":seconds" (including 0), and MAY impose additional limits on that number. See the Security Considerations section of RFC 3834 [RFC3834] for a fuller discussion.

5. IANA Considerations

5.1. Registration of Sieve Extension

   To:  iana@iana.org
   Subject:  Registration of new Sieve extension
   Capability name:  vacation-seconds
   Description:  adds the ":seconds" parameter to the Sieve Vacation
      extension.  Implementations that support this MUST also support
      "vacation".
   RFC number:  RFC 6131
   Contact address:  The Sieve discussion list <sieve@ietf.org>

6. References

6.1. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.
   
   [RFC3834]  Moore, K., "Recommendations for Automatic Responses to
              Electronic Mail", RFC 3834, August 2004.
   
   [RFC5228]  Guenther, P. and T. Showalter, "Sieve: An Email Filtering
              Language", RFC 5228, January 2008.
   
   [RFC5230]  Showalter, T. and N. Freed, "Sieve Email Filtering:
              Vacation Extension", RFC 5230, January 2008.

6.2. Informative References

   [RFC6133]  George, R., Leiba, B., and A. Melnikov, "Sieve Email
              Filtering: Use of Presence Information with Auto-Responder
              Functionality", RFC 6133, July 2011.

Authors' Addresses

   Robins George
   Huawei Technologies
   Bangalore, Karnataka  560071
   India
   
   Phone: +91-080-41117676
   EMail: robinsgv@gmail.com

Barry Leiba
Huawei Technologies

   Phone: +1 646 827 0648
   EMail: barryleiba@computer.org
   URI:   http://internetmessagingtechnology.org/