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This document describes the "environment" extension to the Sieve email filtering language. The "environment" extension gives Sieve access to information about the environment where the Sieve interpreter is running.
Changed one place string result from "UA" to "MUA".
Updated the IANA registration template.
Moved the ihave extension to a separate document.
Added remote-host and remote-ip environment items to the initial set.
Updated references, complete IANA registration templates.
Added text recommending the use of a "name." prefix for groups of items with a common purpose. Also rearranged the text regarding the IANA registry so that the relevant information isn't more centralized.
Sieve [RFC5228] (Guenther, P. and T. Showalter, “Sieve: An Email Filtering Language,” January 2008.) is a language for filtering email messages at or around the time of final delivery. It is designed to be implementable on either a mail client or mail server. It is suitable for running on a mail server where users may not be allowed to execute arbitrary programs, such as on black box Internet Message Access Protocol [RFC3501] (Crispin, M., “INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1,” March 2003.) servers, as it has no user-controlled loops or the ability to run external programs.
Although sieve is intended to be independent of access protocol, mail architecture, and operating system, in some cases it is useful to allow scripts to access information about their execution context. The "environment" extension provides a new environment test that can be used to implement scripts that behave differently when moved from one system to another, when messages arrive from different remote sources or when otherwise operated in different contexts.
"The 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 [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).
The terms used to describe the various components of the Sieve language are taken from [RFC5228] (Guenther, P. and T. Showalter, “Sieve: An Email Filtering Language,” January 2008.) section 1.1.
The capability string associated with the extension defined in this document is "environment".
Usage: environment [COMPARATOR] [MATCH-TYPE]
<name: string>
<key-list: string-list>
The environment test retrieves the item of environment information specified by the name string and matches it to the values specified in the key-list. The test succeeds if a match occurs. The type of match defaults to ":is" and the default comparator is "i;ascii-casemap".
The current message is not a direct source of information for the environment test; the item of information specified by the name string is extracted from the script's operating environment and key-list comes from the script.
The environment test MUST fail unconditionally if the specified information item does not exist. A script MUST NOT fail with an error if the item does not exist. This allows scripts to be written that handle nonexistent items gracefully.
The "relational" extension [RFC5231] (Segmuller, W. and B. Leiba, “Sieve Email Filtering: Relational Extension,” January 2008.) adds a match type called ":count". The count of an environment test is 0 if the environment information returned is the empty string, or 1 otherwise.
Environment items can be standardized or vendor-defined. An IANA registry is defined for both types of items.
The initial set of standardized environment items is as follows:
"domain" => The primary DNS domain associated with the Sieve
execution context, usually but not always a proper
suffix of the host name.
"evaluation-time"
=> Sieve processing is normally performing around or after
the time of final delivery. This item provides
additional information about the relationship to final
delivery. Possible return values are "MTA", meaning the
Sieve is being evaluated before final delivery, "MDA",
meaning evaluation is occurring during final delivery",
and "MUA", meaning evaluation is occurring after final
delivery.
"host" => The fully-qualified domain name of the host where the
Sieve script is executing.
"name" => The product name associated with the Sieve interpreter.
"remote-host"
=> Host name of remote SMTP client, if applicable and
available.
"remote-ip"
=> IP address of remote SMTP client, if applicable and
available.
"version" => The product version associated with the Sieve
interpreter.
Implementations SHOULD support as many of the items on this initial list as possible. Additional standardized items can only be defined in standards-track or experimental RFCs.
Environment item names beginning with "vnd." represent vendor-defined extensions. Such extensions are not defined by Internet standards or RFCs, but are still registered with IANA in order to prevent conflicts.
A registry of environment items is provided by IANA. Item names may be registered on a first-come, first-served basis.
Extensions designed for interoperable use SHOULD be defined in standards track or experimental RFCs. Groups of standardized items MAY choose to use a common name prefix of the form "name.".
Items not defined in a standards track or experimental RFC MUST have a name that begins with the "vnd." prefix and this prefix SHOULD be followed by the name of the vendor or product, such as "vnd.acme.rocket-sled-status".
The following template is to be used for registering new Sieve environment item names with IANA.
To: iana@iana.org
Subject: Registration of new Sieve environment item
Item name: [the string for use in the 'environment' test]
Description: [a brief description of the semantics of the
value the item returns]
RFC number: [for extensions published as RFCs]
Contact address: [email and/or physical address to contact for
additional information]
Multiple items and descripions MAY be specified in a single registration request. Both standardized and vender-defined items use this form.
The environment extension may be used to obtain information about the system the sieve implementation is running on. This information in turn may reveal details about service provider or enterprise infrastructure.
All of the security considerations given in the base Sieve specification also apply to this extension.
The following template specifies the IANA registration of the Sieve extension specified in this document:
To: iana@iana.org
Subject: Registration of new Sieve extension
Capability name: environment
Description: The "environment" extension provides a new
environment test that can be used to implement
scripts that behave differently when moved
from one system to another or otherwise
operated in different contexts.
RFC number: RFC XXXX
Contact address: Sieve discussion list <ietf-mta-filters@imc.org>
This specification also defines a new IANA registry for Sieve environment item names. The specifics of this registry are given in Section 4.3 (IANA Registration of Environment Items). The initial contents of the registry are given in the following section.
The following template specifies the initial IANA registrations for the environment items defined in this document:
To: iana@iana.org
Subject: Registration of new Sieve environment items
Capability name: domain
Description: The primary DNS domain associated with the Sieve
execution context, usually but not always a
proper suffix of the host name.
Capability name: evaluation-time
Description: Time at which this Sieve processing is being
performed.
Capability name: host
Description: The fully-qualified domain name of the host
where the Sieve script is executing.
Capability name: name
Description: The product name associated with the Sieve
interpreter.
Capability name: remote-host
Description: Host name of remote SMTP client, if applicable
and available.
Capability name: remote-ip
Description: IP address of remote SMTP client, if applicable
and available.
Capability name: version
Description: The product version associated with the Sieve
interpreter.
RFC number: RFC XXXX
Contact address: Sieve discussion list <ietf-mta-filters@imc.org>
| [RFC2119] | Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML). |
| [RFC5228] | Guenther, P. and T. Showalter, “Sieve: An Email Filtering Language,” RFC 5228, January 2008 (TXT). |
| [RFC5231] | Segmuller, W. and B. Leiba, “Sieve Email Filtering: Relational Extension,” RFC 5231, January 2008 (TXT). |
| [RFC3501] | Crispin, M., “INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1,” RFC 3501, March 2003 (TXT). |
| Ned Freed | |
| Sun Microsystems | |
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| USA | |
| Phone: | +1 909 457 4293 |
| Email: | ned.freed@mrochek.com |
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