RFC 6134

Sieve Extension: Externally Stored Lists

📅 published July 2011, from ietf

RFC 6134: Sieve Extension: Externally Stored Lists 🎀

Part 1 of 4 💖

Authors: A. Melnikov (Isode Limited) and B. Leiba (Huawei Technologies) 🌸

Category: Standards Track 🦋

ISSN: 2070-1721

Date: July 2011 📅

Obsoletes / Updates: The header doesn't have an "Obsoletes" or "Updates" line, so this RFC doesn't list any. ✨

Abstract

Okay so, the Sieve email filtering language is perfect for whitelists, blacklists, personal distribution lists, and all sorts of other list matching 💅. The catch is that right now every member of those lists has to be hard-coded right into the script 😭. So every time someone joins or leaves a list, you have to edit the script and maybe re-upload it to the mail server. Not ideal, bestie 🙈.

This document defines a Sieve extension for reaching externally stored lists, meaning lists whose members live outside the script. Think LDAP, ACAP, CardDAV (vCard Extensions to WebDAV), or relational databases 🗂️. Main character energy for sure 👑.

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, and it got public review and was approved for publication by the Internet Engineering Steering Group (IESG). If you want more on Internet Standards, check Section 2 of RFC 5741 🧚.

Info about the current status of this document, any errata, and how to send feedback is at http://www.rfc-editor.org/info/rfc6134 💜.

Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. ©️

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents, which you can find at http://trustee.ietf.org/license-info, as they stand on the publication date. Please actually read those, because they spell out your rights and restrictions for this document 📜. Code components pulled from this document must include the Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions, and they come with no warranty, as described in the Simplified BSD License 🌈.

Table of Contents

1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
  1.1.  Conventions Used in This Document  . . . . . . . . . . . .  3
2.  Extlists Extension . . . . . . . . . . . . . . . . . . . . . .  3
  2.1.  Capability Identifier  . . . . . . . . . . . . . . . . . .  3
  2.2.  :list Match Type for Supported Tests . . . . . . . . . . .  3
  2.3.  :list Tagged Argument to the "redirect" Action . . . . . .  5
  2.4.  Other Uses for External Lists  . . . . . . . . . . . . . .  5
  2.5.  Syntax of an Externally Stored List Name . . . . . . . . .  5
  2.6.  Definition of "addrbook" URN Parameter . . . . . . . . . .  7
  2.7.  Test valid_ext_list  . . . . . . . . . . . . . . . . . . .  9
  2.8.  Interaction with ManageSieve . . . . . . . . . . . . . . .  9
  2.9.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . 10
    2.9.1.  Example 1  . . . . . . . . . . . . . . . . . . . . . . 10
    2.9.2.  Example 2  . . . . . . . . . . . . . . . . . . . . . . 10
    2.9.3.  Example 3  . . . . . . . . . . . . . . . . . . . . . . 11
    2.9.4.  Example 4  . . . . . . . . . . . . . . . . . . . . . . 11
    2.9.5.  Example 5  . . . . . . . . . . . . . . . . . . . . . . 11
3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
  4.1.  Registration of Sieve Extension  . . . . . . . . . . . . . 14
  4.2.  Registration of ManageSieve Capability . . . . . . . . . . 14
  4.3.  Creation of Sieve URN Parameters Registry  . . . . . . . . 15
  4.4.  Registration of the "addrbook" URN parameter . . . . . . . 16
  4.5.  Registration of "sieve" URN sub-namespace  . . . . . . . . 16
5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
  6.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
  6.2.  Informative References . . . . . . . . . . . . . . . . . . 17

1. Introduction ✨

This document specifies an extension to the Sieve language [RFC5228] 🧁. It lets you check membership in an external list, or redirect messages to an external list of recipients 💌. An "external list" is a list whose members are stored outside the Sieve script, for example in LDAP [RFC4510], ACAP [RFC2244], CardDAV [CardDAV], or relational databases 🗄️.

The extension adds two things: a new match type that works with supported tests, and a new tagged argument for the "redirect" action 🦋.

1.1. Conventions Used in This Document

Notation conventions follow [RFC5228], Section 1.1, including the use of ABNF [RFC5234] 📝.

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] 🫶.

2. Extlists Extension 🌈

2.1. Capability Identifier

The capability string for this extension is "extlists" 🏷️.

2.2. :list Match Type for Supported Tests

ABNF:

MATCH-TYPE  =/ ":list"
     ; only valid for supported tests

The new ":list" match type changes how the "key-list" parameter (the second parameter) gets read in supported tests 🔍. When you use ":list", the key-list becomes a list of names of externally stored lists. The engine queries those external lists, maybe through some list-specific mechanism, and the test comes back "true" if any of the values you gave matches a member of one or more of those lists 💅.

Comparators are not allowed together with the ":list" match type. So if a test has both, that MUST result in an error 🚫. Queries done through list-specific mechanisms might end up acting like built-in comparators. For example, some lists might be case-sensitive, while others get checked without caring about case 🙈.

Implementations MUST support the use of ":list" in "address", "envelope", and "header" tests. Implementations that include the Variables extension [RFC5229] MUST also support its use in "string" tests 💖.

Implementations MAY support other tests than the ones in this document. Implementations MUST report an error when a script uses ":list" with a test that does not support ":list". This error SHOULD be reported at compile-time, but MAY be reported at run-time. To keep things interoperable, other tests that can be used with ":list" SHOULD be documented in a specification that defines a capability string which can be tested (in a "require" statement or using "ihave" [RFC5463]) 🧩.

For example, testing header ["to", "cc"] against a list makes each "to" and "cc" value get queried, ignoring leading and trailing whitespace 🎀. If any value belongs to the list, the test returns "true". If none of them do, it returns "false". Once a value is found in the list, the query mechanism doesn't need to look any further ⭐.

Some lists let the Sieve engine grab the list and do its own comparison. Other lists don't work that way. They might let you ask whether a value is in the list, but won't let you retrieve the list itself 🔒. It's up to the Sieve implementation to figure out how to talk to any list it supports 🧚. If the Sieve engine is permanently unable to query the list (maybe because the list doesn't support the operation it needs), the test MUST result in a runtime error in the Sieve script 💀.

See Section 2.5 for the detailed syntax used for naming externally stored lists 📖.

The ":list" match type uses "match variables", as defined in Section 3.2 of the Variables extension [RFC5229]. Implementations that also support that extension MUST set the ${0} match variable to the value from the list that matched the query 🎯. Other numbered match variables (${1}, ${2}, and so on) MAY be set with list-specific information that might be useful to the script ✨.

2.3. :list Tagged Argument to the "redirect" Action

Usage:

redirect :list <ext-list-name: string>

The "redirect" action with the ":list" argument sends the message to the set of email addresses in the externally stored list named by the ext-list-name string 📬. This version of redirect is handy for building a personal distribution list 🍓.

For this to work, one of the following conditions has to be true:

  1. The list resolves to a list of email addresses, and the Sieve engine can enumerate those addresses.
  2. The list handler can take care of the redirection on behalf of the Sieve engine.

Say a list contains hashed email address values, or an email address pattern like "sz*@example.com" or "*+ietf@example.net". Then the Sieve engine won't be able to redirect to that list, and the responsibility has to shift over to the list handler 🫠.

If neither the Sieve engine nor the list handler can enumerate (or iterate) the list, or the list doesn't resolve to email addresses, the situation MUST result in a runtime error in the Sieve script 🚨.

See Section 2.5 for the detailed syntax used for naming externally stored lists 🧾.

2.4. Other Uses for External Lists

The uses for external lists specified here are the known cases at the time of writing 🕰️. Other uses, employing other Sieve features, might be invented in the future, and those can be described in extensions to this document 🔮.

2.5. Syntax of an Externally Stored List Name ✨

okay so the name of an externally stored list is ALWAYS an absolute URI [RFC3986] 🔗 Implementations might find URIs like LDAP [RFC4510], CardDAV [CardDAV], or "tag" [RFC4151] super useful for naming external lists 💖

The "tag" URI scheme [RFC4151] is perfect for opaque-but-friendly identifiers 🦋 Resolving them is going to be implementation specific, and it can help hide the messy stuff from end users. For example, an implementation could give you a web interface for managing lists of users stored in LDAP. Making users memorize generic LDAP URI syntax is not very practical, because it's so complicated 😭 So an implementation can use a fixed tag URI prefix such as "tag: example.com,<date>:" (where <date> can be, for example, a date generated once on installation of the web interface and left untouched upon upgrades), and the prefix doesn't even need to be shown to end users 🧚

The "addrbook" URNs defined in Section 2.6 (in particular, the reserved URI "urn:ietf:params:sieve:addrbook:default") MUST be supported 👑 To make registered Sieve URN parameters easier to use, we define a shorthand 💅 A list name that begins with ":" is taken as referencing a Sieve URN parameter, and the initial ":" expands to "urn:ietf:params:sieve:". So we get these equivalences:

:addrbook:default == urn:ietf:params:sieve:addrbook:default

:addrbook:personal == urn:ietf:params:sieve:addrbook:personal

and so on 🌸

The mandatory-to-implement URI is:

urn:ietf:params:sieve:addrbook:default

This one gives access to the user's default address book (usually the personal one) 📇 Note that these are URIs, so normal URI encoding rules apply, including percent-encoding 🫶 The reserved name "default" MUST be considered case-insensitive after decoding. That means all of these are equivalent:

:addrbook:default

:ADDRBOOK:DEFAULT

:aDdRbOOk:DeFauLt

:AddrBook:%44%65%66ault

Address book names other than "default" MAY be case-sensitive, depending upon the implementation, so their case (after URI decoding) MUST be maintained 🎀

It's possible that a server has no access to anything resembling an address book (maybe address books only exist client-side in some implementations), but the server can still provide access to other kinds of lists 🌈 Think of the list of dates in Example 2 (Section 2.9.2), or lists of important keywords and the like. It might sometimes make sense to map ":addrbook:default" onto some available list, but that's not always reasonable 🙈 If there really is no concept of an address book in a particular server implementation, the server MAY support ":addrbook:default" by having all matches to it fail. That SHOULD NOT be done except as a last resort 💀

Queries against address books SHOULD be done without regard to case 🍓

2.6. Definition of "addrbook" URN Parameter 📚

This section gives the details of the "addrbook" Sieve URN parameter that's registered in Section 4.4. URIs that use this parameter begin with "urn:ietf:params:sieve:addrbook:" 🦋

URN parameter name: addrbook

URN parameter syntax: The "addrbook" parameter is defined by the <addrbook-urn> rule, defined using ABNF [RFC5234]:

addrbook-urn = "addrbook:" addrbook [ "?" extensions ]
addrbook = segment
     ; <segment> defined in [RFC3986]
extensions = query
     ; <query> defined in [RFC3986]

Intended usage: "addrbook" URNs are used for designating references to address books. An address book is a concept used by different applications (such as Sieve interpreters) for describing a list of named entries, and it may be translated into other types of address books, such as LDAP groups. Address books may be private or shared; they may be personal, organizational, or perhaps even "crowdsourced" 🫧

The address book name (the "addrbook" element in the ABNF above) refers to a specifically named address book, as defined by the implementation. A user might, for example, have access to a bunch of different address books, like a personal one, a family one, a company one, and one for the town where the user lives 🏘️

The extension information (the "extensions" element in the ABNF above) is available for future extensions. It might allow for things like dynamic subsets of an address book. For example, something like this might be defined in the future:

urn:ietf:params:sieve:addrbook:personal?name.contains=fred

There are no extensions defined at this time.

An "addrbook" URN is designed to be used by applications for referencing address books. Each URN is intended to represent a grouping of addresses that can be logically thought of as one "book". Any given address can belong to more than one book, meaning it can be referred to by more than one URN 🔁

The URI "urn:ietf:params:sieve:addrbook" has no meaning in itself. It MUST be used with sub-parameters representing the address book name and extension information, as shown in the ABNF above 🙅‍♀️

The sub-parameter "default" (creating the URN "urn:ietf:params:sieve:addrbook:default") is a reserved (case-insensitive) name that MUST be implemented, representing a default grouping (book) of addresses. Other names, representing the same or other groupings, MAY be implemented. For example, an implementation might use these sub-parameters:

  • personal -- a book representing the user's personal address book.
  • friends -- a subset of urn:ietf:params:sieve:addrbook:personal, defined by the user.
  • family -- a subset of urn:ietf:params:sieve:addrbook:personal, defined by the user.
  • company -- a book representing the user's company's address book.
  • department -- a subset of urn:ietf:params:sieve:addrbook:company, defined by the company.
  • co-workers -- a subset of urn:ietf:params:sieve:addrbook:company, defined by the user.
  • default -- the default address book, a reference to urn:ietf:params:sieve:addrbook:personal.

Interoperability considerations: Applications are only REQUIRED to support "addrbook:default", where all cases and encodings of "default" are considered equivalent. Address book names other than "default" MAY be case-sensitive, depending upon the implementation, so their case (after URI decoding) MUST be maintained 🤝

Security considerations: Applications SHOULD ensure appropriate restrictions are in place to protect sensitive information that might be revealed by "addrbook" URNs from access or modification by untrusted sources. This one is seriously important, bestie 🚨🔐

Contact: Sieve mailing list <sieve@ietf.org>

2.7. Test valid_ext_list 🧪

Usage: valid_ext_list <ext-list-names: string-list>

The "valid_ext_list" test is true if all of the external list names in the ext-list-names argument are supported, and they're valid both syntactically (including URI parameters) and semantically (including implementation-specific semantic restrictions). Otherwise, the test returns false 💅

This test MUST perform exactly the same validation of an external list name as would be performed by the "header :list" test 🫶

2.8. Interaction with ManageSieve 🌷

This extension defines the following new capability for ManageSieve (see [RFC5804], Section 1.7):

EXTLISTS - A space-separated list of URI schema parts [RFC3986] for supported externally stored list types. This capability MUST be returned if the corresponding Sieve implementation supports the "extlists" extension defined in this document 🎀

This also extends the ManageSieve ABNF as follows:

single-capability  =/ DQUOTE "EXTLISTS" DQUOTE SP ext-list-types CRLF
        ; single-capability is defined in [RFC5804]

ext-list-types  = string
        ; space separated list of URI schema parts
        ; for supported externally stored list types.
        ; MUST NOT be empty.

2.9. Examples 🍭

2.9.1. Example 1 🌟

This example uses a personal address book, along with the Spamtest [RFC5235] and Relational [RFC5231] extensions, to give a different level of spam tolerance to known senders 📬

require ["envelope", "extlists", "fileinto", "spamtest",
         "relational", "comparator-i;ascii-numeric"];
if envelope :list "from" ":addrbook:default"
  { /* Known: allow high spam score */
    if spamtest :value "ge" :comparator "i;ascii-numeric" "8"
      {
        fileinto "spam";
      }
  }
elsif spamtest :value "ge" :comparator "i;ascii-numeric" "3"
  { /* Unknown: less tolerance in spam score */
    fileinto "spam";
  }

The same example can also be written another way, if the Variables extension [RFC5229] is also supported 🧠

require ["envelope", "extlists", "fileinto", "spamtest",
    "variables", "relational", "comparator-i;ascii-numeric"];
if envelope :list "from" ":addrbook:default" {
  set "lim" "8";  /* Known: allow high spam score */
} else {
  set "lim" "3";  /* Unknown: less tolerance in spam score */
}
if spamtest :value "ge" :comparator "i;ascii-numeric" "${lim}" {
  fileinto "spam";
}

2.9.2. Example 2 📅

This example uses the "currentdate" test [RFC5260] and a list containing the dates of local holidays. If today is a holiday, the script will notify (as described in [RFC5435]) the user via the Extensible Messaging and Presence Protocol (XMPP) [RFC5437] about the message 🎉

require ["extlists", "date", "enotify"];
if currentdate :list "date"
   "tag:example.com,2011-01-01:localHolidays" {
   notify "xmpp:romeo@im.example.com";
}

2.9.3. Example 3 💌

This example also uses the "envelope" option [RFC5228] and the Subaddress extension [RFC5233]. If mail is sent with the list name as a subaddress of the recipient (to, say, "alexey+mylist"), and the message comes from a member of the list, it will be redirected to all members of the list. Variants of this technique might be useful for creating private mailing lists 🦋

require ["extlists", "envelope", "subaddress"];

# Submission from list members is sent to all members
if allof (envelope :detail "to" "mylist",
          header :list "from"
                 "tag:example.com,2010-05-28:mylist") {
    redirect :list "tag:example.com,2010-05-28:mylist";
}

2.9.4. Example 4 🚫

This example uses variable matching [RFC5229] to extract the IP address from the last "Received" header field. It then checks that against a "block list" of undesirable IP addresses, and rejects the message if there's a match 🛑

require ["variables", "extlists", "index", "reject"];
if header :index 1 :matches "received" "*(* [*.*.*.*])*" {
    set "ip" "${3}.${4}.${5}.${6}";
    if string :list "${ip}"
        "tag:example.com,2011-04-10:DisallowedIPs" {
        reject "Message not allowed from this IP address";
    }
}

2.9.5. Example 5 🦋

okay this one is giving security guard energy 🛡️ it uses a bunch of the MIME parts extension [RFC5703] features to scan for unsafe attachment types. the unsafe types live in an external list, so every user and every script can share the same list, and nobody has to touch the scripts when the list changes. iconic 💅

[Note that this is an illustrative example, and more rigorous malware filtering is advisable. It is insufficient to base email security on checks of filenames alone.] translation: this is a demo, not a full malware shield 🙈 and filenames alone are not security, bestie
       require [ "extlists", "foreverypart", "mime", "enclose" ];

       foreverypart
       {
         if header :mime :param "filename"
            :list ["Content-Type", "Content-Disposition"]
              "tag:example.com,2011-04-10:BadFileNameExts"
         {
           # these attachment types are executable
           enclose :subject "Warning" :text
    WARNING! The enclosed message has attachments that might be unsafe.
    These attachment types may contain a computer virus program
    that can infect your computer and potentially damage your data.

    Before clicking on these message attachments, you should verify
    with the sender that this message was sent intentionally, and
    that the attachments are safe to open.
    .
    ;
           break;
         }
       }

3. Security Considerations 🔒

okay security time, and it's a whole thing 😭 the security considerations for the "address"/"envelope"/"header" tests and the "redirect" action from Sieve [RFC5228] also apply to this document, so bring them along 🫶

external list memberships ought to be treated as if they're an integral part of the script 💜 which means a temporary failure to access an external list SHOULD be handled the same way as a temporary failure to retrieve the Sieve script itself.

for example, say the Sieve script is stored in the Lightweight Directory Access Protocol [RFC4510] and it can't be retrieved when a message comes in (maybe the LDAP server is down 💀). then the Sieve engine might delay message delivery until the script can be retrieved successfully. similarly, if an external list is stored in LDAP and that LDAP server is unavailable, the Sieve engine would take the same action: delay message delivery and try again later ✨

Protocols/APIs used to retrieve/verify external list membership MUST provide an appropriate level of confidentiality and authentication. usually that's at least the same level of confidentiality as the protocols/APIs used to fetch Sieve scripts, but only the implementation (or deployment) knows what's actually appropriate 🎀 think of it like this: an LDAP request on a closed LAN that only talks to trusted servers might need neither encryption nor authentication, on a firewalled LAN inside a company it might be OK to skip encryption depending on policy, and on the open Internet, encryption and authentication are probably both required. it also matters whether the list is private or public, since no encryption or authentication may be needed for public data, even on the Internet 🌸

having the processing and outcome of a script depend on external data can let someone who controls that data have unusual, and maybe unauthorized, control over the script, and therefore over what happens to the user's email 😱 a user relying on a list for spam control might find important mail getting discarded because the list was tampered with. someone using redirect to an external list could have her email sent to the wrong eyes because of that same tampering. security and integrity protection of external lists is just as important as protection of the Sieve script itself 🔥

implementations of this extension should keep in mind that matching values against an externally stored list can be I/O and/or CPU intensive 🙃 that can be used to deny service to the mail server and/or to the servers providing access to externally stored mailing lists. a naive implementation, like one that tries to retrieve the whole list just to do matching, can make this worse.

but note that many protocols that can be used for accessing externally stored lists support flexible searching features that can be used to minimize network traffic and load on the directory service. for example, LDAP allows for search filters. implementations SHOULD use such features whenever they can ✨

many organizations support external lists with thousands of recipients 🍓 so to avoid mailbombs when redirecting a message to an externally stored list, implementations SHOULD enforce limits on the number of recipients and/or on the domains those recipients belong to 💣

note, in particular, that it's way too easy for a script to do this:

redirect :list ":addrbook:default";

and that sends messages to "everyone in your address book" 😬 you can easily imagine both intentional and accidental abuse. it can be even worse for something like ":addrbook:corporate". warnings, as well as enforced limits, are appropriate here 🚨

applications SHOULD ensure appropriate restrictions are in place to protect sensitive information that might be revealed by "addrbook" URNs from access or modification by untrusted sources 🔐

4. IANA Considerations 📋

4.1. Registration of Sieve Extension

okay so this is the template for registering the Sieve extension in this document. the information has been added to the Sieve Extensions registry at http://www.iana.org ✨

   To: iana@iana.org

   Subject:  Registration of new Sieve extension

   Capability name:  extlists

   Description:  Adds the ":list" match type to certain Sieve tests, and
       the ":list" argument to the "redirect" action.  The ":list" match
       type changes tests to match values against values stored in one
       or more externally stored lists.  The ":list" argument to the
       redirect action changes the redirect action to forward the
       message to email addresses stored in the externally stored list.

   RFC number:  RFC 6134

   Contact address:  Sieve mailing list <sieve@ietf.org>

4.2. Registration of ManageSieve Capability

IANA registered a new ManageSieve Capability using the IANA registration template from [RFC5804], and it looks like this 💖

   To: iana@iana.org

   Subject:  ManageSieve Capability Registration

   Capability name:  extlists

   Description:  This capability is returned if the server supports the
       "extlists" RFC 6134 Sieve extension.

   Relevant publications:  RFC 6134, Section 2.8
   Person & email address to contact for further information:
       Sieve mailing list <sieve@ietf.org>

   Author/Change controller:  IESG

4.3. Creation of Sieve URN Parameters Registry

IANA created a new registry under "Sieve Extensions" for Sieve URN Parameters 🎀 registration into it follows the "Specification Required" policy from [RFC5226].

the registry has two items:

  • URN parameter name: the name of the URN parameter. if the name is "paramname", the resulting top-level URN will be urn:ietf:params:sieve:paramname.
  • Reference: the document and section where the definition of the parameter can be found. include the section number as well as the document reference, so the documentation is easy to find.

the documentation (which lives in the referenced document and section, and is not included in the registry) MUST include the following information (see Section 2.6 for an example):

  • URN parameter name: the name of the URN parameter.
  • URN parameter syntax: the syntax of the parameter and any sub-parameters, which SHOULD be specified using ABNF [RFC5234].
  • Intended usage: a detailed description of how the parameter and any sub-parameters are expected to be used. this is the place to define static sub-parameters, registries for sub-parameters, options, registries for options, and so on.
  • Interoperability considerations: any notes specific to interoperability issues. this is where to put mandatory-to-implement sub-parameters and the like.
  • Security considerations: any notes specific to security and privacy issues.
  • Contact: contact information, in case there are questions.

4.4. Registration of the "addrbook" URN parameter

IANA registered a new Sieve URN parameter in the registry defined in Section 4.3 🧚

   URN parameter name:  addrbook

   Reference:  RFC 6134, Section 2.6

4.5. Registration of "sieve" URN sub-namespace

IANA registered a new URN sub-namespace within the IETF URN Sub-namespace for Registered Protocol Parameter Identifiers defined in [RFC3553] 🌈

   Registry name:  sieve

   Specification:  RFC 6134

   Repository:  Sieve URN Parameters registry (Section 4.3)

   Index value:  Sub-parameters MUST be specified in UTF-8, using
       standard URI encoding where necessary.

5. Acknowledgements 🫶

thanks to Alexandros Vellis, Nigel Swinson, Ned Freed, Kjetil Torgrim Homme, Dave Cridland, Cyrus Daboo, Pete Resnick, and Robert Burrell Donkin for the ideas, comments, and suggestions 💜 Kristin Hubner also helped a ton with the examples, so she's an icon 👑

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.
  • [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005.
  • [RFC4151] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme", RFC 4151, October 2005.
  • [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
  • [RFC5228] Guenther, P. and T. Showalter, "Sieve: An Email Filtering Language", RFC 5228, January 2008.
  • [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008.
  • [RFC5804] Melnikov, A. and T. Martin, "A Protocol for Remotely Managing Sieve Scripts", RFC 5804, July 2010.

6.2. Informative References 📚

okay bestie, this is the extra-credit reading list for the nerds who want more 🤓🫶

  • [CardDAV] Daboo, C., "vCard Extensions to WebDAV (CardDAV)", Work in Progress, November 2009.
  • [RFC2244] Newman, C. and J. Myers, "ACAP -- Application Configuration Access Protocol", RFC 2244, November 1997.
  • [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An IETF URN Sub-namespace for Registered Protocol Parameters", BCP 73, RFC 3553, June 2003.
  • [RFC4510] Zeilenga, K., "Lightweight Directory Access Protocol (LDAP): Technical Specification Road Map", RFC 4510, June 2006.
  • [RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension", RFC 5229, January 2008.
  • [RFC5231] Segmuller, W. and B. Leiba, "Sieve Email Filtering: Relational Extension", RFC 5231, January 2008.
  • [RFC5233] Murchison, K., "Sieve Email Filtering: Subaddress Extension", RFC 5233, January 2008.
  • [RFC5235] Daboo, C., "Sieve Email Filtering: Spamtest and Virustest Extensions", RFC 5235, January 2008.
  • [RFC5260] Freed, N., "Sieve Email Filtering: Date and Index Extensions", RFC 5260, July 2008.
  • [RFC5435] Melnikov, A., Leiba, B., Segmuller, W., and T. Martin, "Sieve Email Filtering: Extension for Notifications", RFC 5435, January 2009.
  • [RFC5437] Saint-Andre, P. and A. Melnikov, "Sieve Notification Mechanism: Extensible Messaging and Presence Protocol (XMPP)", RFC 5437, January 2009.
  • [RFC5463] Freed, N., "Sieve Email Filtering: Ihave Extension", RFC 5463, March 2009.
  • [RFC5703] Hansen, T. and C. Daboo, "Sieve Email Filtering: MIME Part Tests, Iteration, Extraction, Replacement, and Enclosure", RFC 5703, October 2009.

Authors' Addresses 🎀

here's where you can find the people who wrote this whole thing, lowkey the real MVPs 👑

Alexey Melnikov
Isode Limited
5 Castle Business Village
36 Station Road
Hampton, Middlesex  TW12 2BX
UK

EMail: Alexey.Melnikov@isode.com


Barry Leiba
Huawei Technologies

Phone: +1 646 827 0648
EMail: barryleiba@computer.org
URI:   http://internetmessagingtechnology.org/
📦 where this page comes from