Internet DRAFT - draft-billon-expires
draft-billon-expires
Network Working Group B. Billon
Internet-Draft Splio
Intended status: Standards Track J. Levine
Expires: 14 June 2023 Standcore LLC
11 December 2022
Updated Use of the Expires Message Header Field
draft-billon-expires-08
Abstract
This document allows broader use of the Expires message header field
for mail messages. Message creators can then indicate when a message
loses its validity, while recipients would use the information to
ignore or change the display of these messages.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 14 June 2023.
Copyright Notice
Copyright (c) 2022 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 (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Billon & Levine Expires 14 June 2023 [Page 1]
Internet-Draft expires December 2022
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Header Field definition . . . . . . . . . . . . . . . . . . . 2
3. Advice to Message Creators . . . . . . . . . . . . . . . . . 3
4. Advice to Message Readers . . . . . . . . . . . . . . . . . . 3
5. Security considerations . . . . . . . . . . . . . . . . . . . 3
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. Normative References . . . . . . . . . . . . . . . . . . . . 4
9. Informative References . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
[RFC2156] defined a mapping of header fields between X.400 and
RFC822/MIME. One of the mapped fields is the "Expires" header field,
which provides a date and time at which a message is considered to
lose its validity.
Netnews articles [RFC5536] have an Expires header with a similar
slightly more strict syntax and similar meaning.
This document extends the use of the "Expires" header field to
Internet email in general, whether the message comes from an X.400
gateway or elsewhere.
The date and time of expiration can be used by the mailbox provider
or the MUA to indicate to the user that certain messages could be de-
emphasized or not shown to the user, to unclutter the user's mailbox.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Header Field definition
The header field definition remains the same as in [RFC2156] and
[RFC4021]. It indicates the time at which a message loses its
validity. Using the ABNF from [RFC5322], its syntax is:
expires = "Expires:" date-time CRLF
Example:
Expires: Wed, 1 Dec 2021 17:22:57 +0000
Billon & Levine Expires 14 June 2023 [Page 2]
Internet-Draft expires December 2022
Message creators MUST NOT include more than one Expires header field
in the message they send.
If there is more than one Expires header field then message readers
SHOULD act as if no Expires header field is present.
3. Advice to Message Creators
Message creators add the header field along with a relevant date and
time when they know that the message loses its validity. This could
apply to commercial newsletters that include time-limited offers,
event announcements, social notifications, and periodic announcement
messages.
4. Advice to Message Readers
Message readers, such as mailbox providers, web mail and MUAs could
de-emphasize the display of expired messages or determine not do
display them. They could allow users to control the actions to take
for expired messages.
The information provided in the header field is intended to be used
as a signal to provide an improved experience to the end-user. For
instance, systems might allow automatic rules to clean up expired
email from specific message creators or with defined characteristics,
or to provide a mode to quickly handle all expired email.
5. Security considerations
A message creator can put any date in an Expires header field,
including dates in the distant past or future. Without further
knowledge about the message creator, recipient systems and message
readers cannot assume that the contents of the header are accurate or
benign.
For example, a malicious message creator might send spam mail that
includes a expiry date in the past, in the hope that recipients will
not see or report the mail, and then adaptive spam filters would use
it as non-spam training material. A creator might include a date in
the immediate future in the hope that a recipient would see and act
on a message, but could not find it later to complain about it. Or a
creator might include a date in the distant future in the hope that
the message would stay in a recipient's inbox and would be more
likely to be read.
While the header field can be useful to determine how to display a
message to a user, it is unlikely to be useful to determine whether
or not the message is wanted or is fraudulent.
Billon & Levine Expires 14 June 2023 [Page 3]
Internet-Draft expires December 2022
6. Acknowledgements
This document was informed by discussions with and/or contributions
from Barry Leiba, Alexey Melnikov, Jonathan Loriaux, Charles Sauthier
and Simon Bressier.
7. IANA Considerations
IANA is requested to update an existing entry in the Permanent
Message Headers Field Names registry
(https://www.iana.org/assignments/message-headers/message-
headers.xhtml)
Header field name: Expires
Applicable protocol: mail
Status: standard
Author/Change controller: IETF
Specification document: this document
8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2156] Kille, S., "MIXER (Mime Internet X.400 Enhanced Relay):
Mapping between X.400 and RFC 822/MIME", RFC 2156,
DOI 10.17487/RFC2156, January 1998,
<https://www.rfc-editor.org/info/rfc2156>.
[RFC4021] Klyne, G. and J. Palme, "Registration of Mail and MIME
Header Fields", RFC 4021, DOI 10.17487/RFC4021, March
2005, <https://www.rfc-editor.org/info/rfc4021>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/info/rfc5322>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9. Informative References
Billon & Levine Expires 14 June 2023 [Page 4]
Internet-Draft expires December 2022
[RFC5536] Murchison, K., Ed., Lindsey, C., and D. Kohn, "Netnews
Article Format", RFC 5536, DOI 10.17487/RFC5536, November
2009, <https://www.rfc-editor.org/info/rfc5536>.
Authors' Addresses
Benjamin Billon
Splio
Email: bbillon@splio.com
John Levine
Standcore LLC
Email: standards@standcore.com
Billon & Levine Expires 14 June 2023 [Page 5]
