Sieve: A Mail Filtering Language (RFC3028)

Network Working Group T. Showalter Request for Comments: 3028 Mirapoint, Inc. Category: Standards Track January 2001

Sieve: A Mail Filtering Language

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.

Copyright Notice

Copyright (C) The Internet Society (2001). All Rights Reserved.

Abstract

This document describes a language for filtering e-mail messages at time of final delivery. It is designed to be implementable on either a mail client or mail server. It is meant to be extensible, simple, and independent of access protocol, mail architecture, and operating system. 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 (IMAP) servers, as it has no variables, loops, or ability to shell out to external programs.

Table of Contents

1. Introduction ........................................... 3 1.1. Conventions Used in This Document ..................... 4 1.2. Example mail messages ................................. 4 2. Design ................................................. 5 2.1. Form of the Language .................................. 5 2.2. Whitespace ............................................ 5 2.3. Comments .............................................. 6 2.4. Literal Data .......................................... 6 2.4.1. Numbers ............................................... 6 2.4.2. Strings ............................................... 7 2.4.2.1. String Lists .......................................... 7 2.4.2.2. Headers ............................................... 8 2.4.2.3. Addresses ............................................. 8 2.4.2.4. MIME Parts ............................................ 9 2.5. Tests ................................................. 9 2.5.1. Test Lists ............................................ 9

Showalter Standards Track [Page 1]

RFC 3028 Sieve: A Mail Filtering Language January 2001

2.6. Arguments ............................................. 9 2.6.1. Positional Arguments .................................. 9 2.6.2. Tagged Arguments ...................................... 10 2.6.3. Optional Arguments .................................... 10 2.6.4. Types of Arguments .................................... 10 2.7. String Comparison ..................................... 11 2.7.1. Match Type ............................................ 11 2.7.2. Comparisons Across Character Sets ..................... 12 2.7.3. Comparators ........................................... 12 2.7.4. Comparisons Against Addresses ......................... 13 2.8. Blocks ................................................ 14 2.9. Comman...