Sieve Email Filtering: Spamtest and Virustest Extensions
RFC 5235
Document | Type |
RFC - Proposed Standard
(January 2008; No errata)
Obsoletes RFC 3685
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Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text pdf html bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 5235 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Lisa Dusseault | ||
Send notices to | (None) |
Network Working Group C. Daboo Request for Comments: 5235 January 2008 Obsoletes: 3685 Category: Standards Track Sieve Email Filtering: Spamtest and Virustest Extensions Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract The Sieve email filtering language "spamtest", "spamtestplus", and "virustest" extensions permit users to use simple, portable commands for spam and virus tests on email messages. Each extension provides a new test using matches against numeric "scores". It is the responsibility of the underlying Sieve implementation to do the actual checks that result in proper input to the tests. Table of Contents 1. Introduction and Overview .......................................2 2. Conventions Used in This Document ...............................2 3. Sieve Extensions ................................................3 3.1. General Considerations .....................................3 3.2. Test spamtest ..............................................3 3.2.1. spamtest without :percent Argument ..................4 3.2.2. spamtest with :percent Argument .....................5 3.3. Test virustest .............................................7 4. Security Considerations .........................................9 5. IANA Considerations .............................................9 5.1. spamtest Registration ......................................9 5.2. virustest Registration ....................................10 5.3. spamtestplus Registration .................................10 6. References .....................................................10 6.1. Normative References ......................................10 6.2. Informative References ....................................11 Appendix A. Acknowledgments .......................................12 Appendix B. Important Changes since RFC 3685 ......................12 Daboo Standards Track [Page 1] RFC 5235 Sieve: Spamtest and Virustest Extensions January 2008 1. Introduction and Overview Sieve scripts are frequently being used to do spam and virus filtering either based on implicit script tests (e.g., tests for "black-listed" senders directly encoded in the Sieve script), or via testing messages modified by some external spam or virus checker that handled the message prior to Sieve. The use of third-party spam and virus checker tools poses a problem since each tool has its own way of indicating the result of its checks. These usually take the form of a header added to the message, the content of which indicates the status using some syntax defined by the particular tool. Each user has to then create their own Sieve scripts to match the contents of these headers to do filtering. This requires the script to stay in synchronization with the third-party tool as it gets updated or perhaps replaced with another. Thus, scripts become tied to specific environments and lose portability. The purpose of this document is to introduce two Sieve tests that can be used to implement "generic" tests for spam and viruses in messages processed via Sieve scripts. The spam and virus checks themselves are handled by the underlying Sieve implementation in whatever manner is appropriate, so that the Sieve spam and virus test commands can be used in a portable way. In order to do numeric comparisons against the returned strings, server implementations MUST also support the Sieve relational [RFC5231] extension, in addition to the extensions described here. All examples below assume the relational extension is present. 2. Conventions Used in This Document Conventions for notations are as in [RFC5228] Section 1.1. 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]. The term "spam" is used in this document to refer to unsolicited or unwanted email messages. This document does not attempt to define what exactly constitutes spam, or how it should be identified, or what actions should be taken when detected. The term "virus" is used in this document to refer to any type of message whose content can cause malicious damage. This document does not attempt to define what exactly constitutes a virus, or how it should be identified, or what actions should be taken when detected.Show full document text