Request for Comments: 6131
Category: Standards Track
Sieve Vacation Extension: "Seconds" Parameter
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.
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Table of Contents
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
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>
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 ["email@example.com", "firstname.lastname@example.org"] :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: email@example.com 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 <firstname.lastname@example.org>
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
Robins George Huawei Technologies Bangalore, Karnataka 560071 India Phone: +91-080-41117676 EMail: email@example.com
Phone: +1 646 827 0648 EMail: firstname.lastname@example.org URI: http://internetmessagingtechnology.org/