RFC 5788
IMAP4 Keyword Registry
RFC 5788: IMAP4 Keyword Registry 🎀
Okay bestie, this is RFC 5788 🦋 It's an Internet Standards Track document (so it's official, not just an opinion) from March 2010, with ISSN 2070-1721. The authors are A. Melnikov and D. Cridland, both from Isode Limited. The header doesn't list anything it obsoletes or updates, so it's a fresh start 💖
Abstract ✨
The goal here is to set up a brand new IANA registry for IMAP keywords and define how keywords get registered. The whole point is better interoperability between different IMAP clients, so everyone's on the same page 🫶
Status of This Memo 💅
This is an Internet Standards Track document. It's a product of the Internet Engineering Task Force (IETF) and represents the consensus of the IETF community. It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). For more on Internet Standards, check out Section 2 of RFC 5741 📚
For the current status, any errata, and how to give feedback, head to http://www.rfc-editor.org/info/rfc5788 🌸
Copyright Notice 🌈
Copyright (c) 2010 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 (http://trustee.ietf.org/license-info) as they were in effect on the date of publication. Please actually read these, because they describe your rights and restrictions for this document 🙈 Code Components pulled out of this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come without warranty as described in the Simplified BSD License.
Table of Contents 🧚
1. Introduction ....................................................2
2. Conventions Used in This Document ...............................2
3. IANA Considerations .............................................3
3.1. Review Guidelines for the Designated Expert Reviewer .......4
3.2. Comments on IMAP Keywords' Registrations ...................5
3.3. Change Control .............................................5
3.4. Initial Registrations ......................................6
3.4.1. $MDNSent IMAP Keyword Registration ..................6
3.4.2. $Forwarded IMAP Keyword Registration ................7
3.4.3. $SubmitPending IMAP Keyword Registration ............8
3.4.4. $Submitted IMAP Keyword Registration ................9
4. Security Considerations ........................................10
5. Acknowledgements ...............................................10
6. References .....................................................10
6.1. Normative References ......................................10
6.2. Informative References ....................................111. Introduction 💖
Okay so, IMAP keywords [RFC3501] are boolean named flags that clients use to annotate messages in an IMAP mailbox. Keywords are an optional feature of IMAP, but most IMAP servers can store arbitrary keywords anyway. Plenty of mainstream clients only use a limited set of specific keywords, and some can manage arbitrary ones (create, edit, display) ✨
Over the years some keywords became de-facto standards with specific semantics attached. Sometimes different client implementors picked different names for the same semantics 🙈 Some server implementors automatically map those keywords to each other so clients can still talk to each other, which is honestly iconic of them 👑
Other times the same keyword got used with different semantics, and that caused interoperability problems 💀
This document is here to stop more incompatible uses of IMAP keywords. It sets up an "IMAP Keywords" registry and allocates a special prefix for standardized keywords 🦋
2. Conventions Used in This Document 📝
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 RFC 2119 [Kwds] 🫶
3. IANA Considerations 🌸
IANA has established a brand new registry for IMAP keywords ✨
To register an IMAP keyword, you fill in the template below and then follow the instructions on the IANA pages for the registry to submit it to IANA 📝
Subject: Registration of IMAP keyword X
IMAP keyword name:
Purpose (description):
Private or Shared on a server: (One of PRIVATE, SHARED, or BOTH.
PRIVATE means that each different
user has a distinct copy of the
keyword. SHARED means that all
different users see the same value of
the keyword. BOTH means that an IMAP
server can have the keyword as either
private or shared.)
Is it an advisory keyword or may it cause an automatic action:
When/by whom the keyword is set/cleared:
Related keywords: (for example, "mutually exclusive with keywords Y
and Z")
Related IMAP capabilities:
Security considerations:
Published specification (recommended):
Person & email address to contact for further information:
Intended usage: (One of COMMON, LIMITED USE, or DEPRECATED (i.e.,
not recommended for use))
Owner/Change controller: (MUST be "IESG" for any "common use"
keyword registration specified in an IETF
Review document. See definition of "common
use" below in this section. When the
Owner/Change controller is not a
Standardization Organization, the
registration request MUST make it clear if
the registration is controlled by a
company, or the individual performing the
registration.)
Note: (Any other information that the author deems interesting
may be added here, for example, if the keyword(s) is
supported by existing clients.)Registering an IMAP keyword requires Expert Review [RFC5226] 🔍 You kick it off by posting your registration request to the Message Organization WG mailing list <morg@ietf.org> (or whatever replacement the responsible Application Area Director picked), and you CC IANA at <iana@iana.org> 💌 Then the community gets at least two weeks to give input on that mailing list. After that, the expert decides whether the request is appropriate and either approves or disapproves it, with notice to the requestor, the mailing list, and IANA. Any refusal comes with a clear explanation 🫶
The IESG appoints one or more Expert Reviewers for the IMAP keyword registry set up by this document 👑
Expert Reviewers should aim for timely reviews. They should take no longer than six weeks to make and announce a decision, or let the mailing list know that more time is needed ⏰
Decisions (or lack of decisions) made by an Expert Reviewer can first be appealed to the Application Area Directors. If the appellant isn't satisfied with that response, they can go to the full IESG 🔥
There are two types of IMAP keywords in the "IMAP Keywords" registry: ones intended for "common use", and vendor-/organization-specific ones (also known as "limited use"). An IMAP keyword counts as "common use" if it's reasonably expected to be implemented in at least two independent client implementations. The two types have different levels of registration requirements, so keep reading 🌈
3.1. Review Guidelines for the Designated Expert Reviewer 💅
Expert Reviewers should focus on the following requirements ✨
Registering a vendor-/organization-specific ("limited use") IMAP keyword is easier. The Expert Reviewer only needs to check that the requested name doesn't conflict with a name that's already registered, and that the name isn't too generic, misleading, etc. The Expert Reviewer MAY request a change to the IMAP keyword name before approving the registration. The Expert Reviewer SHOULD refuse a registration if there's already a registered IMAP keyword that serves the same purpose but has a different name 🙅♀️
When registering an IMAP keyword for "common use", the Expert Reviewer does all the checks described for vendor-/organization-specific keywords, plus the extra checks detailed below 🎀
Keywords intended for "common use" SHOULD start with the "$" prefix. (This is a SHOULD and not a MUST, because some commonly used IMAP keywords that are in widespread use don't follow this convention 🙈)
IMAP keywords intended for "common use" SHOULD be standardized in IETF Review [RFC5226] documents. (IETF Review documents still require Expert Review, so no skipping that step 😤)
Values in the "IMAP Keywords" IANA registry that are intended for "common use" must be clearly documented and likely to ensure interoperability. They must be useful and not harmful to the Internet 🌸 When an IMAP keyword being registered is already deployed, Expert Reviewers should favor registering it over demanding perfect documentation and/or asking for a name change 🫶
The Expert Reviewer MAY automatically "upgrade" a registration request for a "limited use" IMAP keyword to "common use" level. The Expert Reviewer MAY also request that a registration targeted for "common use" be registered as "limited use" instead 🦋
Part 2 picks up at Section 3.2 with comments on registrations, change control, and the rest of the bestie-approved content 💖
3.4. Initial Registrations 🎀
IANA has registered the IMAP keywords specified in the following subsections in the registry established by this document. 🧚
3.4.1. $MDNSent IMAP Keyword Registration 💌
Subject: Registration of IMAP keyword $MDNSent
IMAP keyword name: $MDNSent
Purpose (description): okay so this one says a Message Disposition Notification (MDN) MUST NOT be sent for any message tagged with the $MDNSent IMAP keyword. Like, hard no, bestie. 🙅♀️
Private or Shared on a server: SHARED ✨
Is it an advisory keyword or may it cause an automatic action: this keyword can cause automatic action by the client. See [RFC3503] for more details. 🤖
When/by whom the keyword is set/cleared: this keyword is set by an IMAP client when it decides to act on an MDN request, or when uploading a sent or draft message. It can also be set by a delivery agent. Once it's set, the flag SHOULD NOT be cleared. 🔒
Related keywords: None
Related IMAP capabilities: None
Security considerations: See Section 6 of [RFC3503] 🛡️
Published specification (recommended): [RFC3503]
Person & email address to contact for further information: Alexey Melnikov <alexey.melnikov@isode.com> 📮
Intended usage: COMMON
Owner/Change controller: IESG 👑
Note:
3.4.2. $Forwarded IMAP Keyword Registration 🦋
Subject: Registration of the IMAP keyword $Forwarded
IMAP keyword name: $Forwarded
Purpose (description): $Forwarded is used by several IMAP clients to specify that the message was resent to another email address, embedded within or attached to a new message. This keyword is set by the mail client when it successfully forwards the message to another email address. Typically it's how a client shows a different (or additional) icon for a message that got forwarded. 💫
Private or Shared on a server: BOTH
Is it an advisory keyword or may it cause an automatic action: advisory 💁♀️
When/by whom the keyword is set/cleared: this keyword can be set by either a delivery agent or a mail client. Once it's set, the flag SHOULD NOT be cleared. Notes: there is no way to tell if a message with the $Forwarded keyword set was forwarded more than once. 🤷♀️
Related keywords: None
Related IMAP capabilities: None
Security considerations: A server implementing this keyword as a shared keyword may disclose that a confidential message was forwarded. 🫣
Published specification (recommended): [RFC5550]
Person & email address to contact for further information: Alexey Melnikov <alexey.melnikov@isode.com> 📮
Intended usage: COMMON
Owner/Change controller: IESG 👑
Note:
3.4.3. $SubmitPending IMAP Keyword Registration 🚀
Subject: Registration of IMAP keyword $SubmitPending
IMAP keyword name: $SubmitPending
Purpose (description): the $SubmitPending IMAP keyword marks the message as awaiting submission. It lets you store messages that are waiting to be sent in the same mailbox as messages that were already submitted and/or are still being edited. 📬
A message that has both $Submitted and $SubmitPending IMAP keywords set is a message being actively submitted. 🏃♀️
Private or Shared on a server: SHARED
Is it an advisory keyword or may it cause an automatic action: this keyword can cause automatic action by the client. See Section 5.10 of [RFC5550] for more details. ⚡
When/by whom the keyword is set/cleared: this keyword is set by a mail client when it decides the message needs to be sent out. 📤
Related keywords: $Submitted
Related IMAP capabilities: None
Security considerations: A server implementing this keyword as a shared keyword may disclose that a confidential message is scheduled to be sent out or is being actively sent out. 😬
Published specification (recommended): [RFC5550]
Person & email address to contact for further information: Alexey Melnikov <alexey.melnikov@isode.com> 📮
Intended usage: COMMON
Owner/Change controller: IESG 👑
Note:
3.4.4. $Submitted IMAP Keyword Registration 🌷
Subject: Registration of IMAP keyword $Submitted
IMAP keyword name: $Submitted
Purpose (description): the $Submitted IMAP keyword marks the message as being sent out.
A message that has both $Submitted and $SubmitPending IMAP keywords set is a message being actively submitted. 🏃♀️
Private or Shared on a server: SHARED
Is it an advisory keyword or may it cause an automatic action: this keyword can cause automatic action by the client. See Section 5.10 of [RFC5550] for more details. ⚡
When/by whom the keyword is set/cleared: this keyword is set by a mail client when it decides to start sending it. 🖱️
Related keywords: $SubmitPending
Related IMAP capabilities: None
Security considerations: A server implementing this keyword as a shared keyword may disclose that a confidential message was sent or is being actively sent out. 🫢
Published specification (recommended): [RFC5550]
Person & email address to contact for further information: Alexey Melnikov <alexey.melnikov@isode.com> 📮
Intended usage: COMMON
Owner/Change controller: IESG 👑
Note:
4. Security Considerations 🔐
IMAP keywords are one of the base IMAP features [RFC3501]. This document doesn't change their behavior, so it does not add new security issues. 🙌
A particular IMAP keyword might have specific security considerations, which are documented in the IMAP keyword registration template standardized by this document. 📋
5. Acknowledgements 💖
The creation of this document was prompted by one of many discussions on the IMAP mailing list. 💬
John Neystadt co-authored the first version of this document. 🫶
Special thanks to Chris Newman, David Harris, Lyndon Nerenberg, Mark Crispin, Samuel Weiler, Alfred Hoenes, Lars Eggert, and Cullen Jennings for reviewing different versions of this document. However, all errors or omissions must be attributed to the authors of this document. 🙏
The authors would also like to thank the developers of Mozilla mail clients for providing food for thought. 🦊
6. References 📚
6.1. Normative References
[Kwds] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.6.2. Informative References
[RFC3503] Melnikov, A., "Message Disposition Notification (MDN)
profile for Internet Message Access Protocol (IMAP)",
RFC 3503, March 2003.
[RFC5550] Cridland, D., Melnikov, A., and S. Maes, "The Internet
Email to Support Diverse Service Environments (Lemonade)
Profile", RFC 5550, August 2009.Authors' Addresses 🧚♀️
Alexey Melnikov
Isode Limited
5 Castle Business Village
36 Station Road
Hampton, Middlesex TW12 2BX
UK
EMail: Alexey.Melnikov@isode.com
URI: http://www.melnikov.ca/
Dave Cridland
Isode Limited
5 Castle Business Village
36 Station Road
Hampton, Middlesex TW12 2BX
UK
EMail: dave.cridland@isode.com📦 where this page comes from
- ietf: rfc5788 2010-03
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms