7Internet Engineering Task Force (IETF) K. Murchison
8Request for Comments: 8580 B. Gondwana
9Updates: 5230, 5435 FastMail
10Category: Standards Track May 2019
14 Sieve Extension: File Carbon Copy (FCC)
18 The Sieve email filtering language provides a number of action
19 commands, some of which can generate additional messages on behalf of
20 the user. This document defines an extension to such commands to
21 allow a copy of any generated message to be filed into a target
24 This document updates RFCs 5230 and 5435 by adding a new tagged
25 argument to the Vacation and Notify actions, respectively.
29 This is an Internet Standards Track document.
31 This document is a product of the Internet Engineering Task Force
32 (IETF). It represents the consensus of the IETF community. It has
33 received public review and has been approved for publication by the
34 Internet Engineering Steering Group (IESG). Further information on
35 Internet Standards is available in Section 2 of RFC 7841.
37 Information about the current status of this document, any errata,
38 and how to provide feedback on it may be obtained at
39 https://www.rfc-editor.org/info/rfc8580.
43 Copyright (c) 2019 IETF Trust and the persons identified as the
44 document authors. All rights reserved.
46 This document is subject to BCP 78 and the IETF Trust's Legal
47 Provisions Relating to IETF Documents
48 (https://trustee.ietf.org/license-info) in effect on the date of
49 publication of this document. Please review these documents
50 carefully, as they describe your rights and restrictions with respect
51 to this document. Code Components extracted from this document must
52 include Simplified BSD License text as described in Section 4.e of
53 the Trust Legal Provisions and are provided without warranty as
54 described in the Simplified BSD License.
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60RFC 8580 Sieve Extension: FCC May 2019
65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
66 2. Conventions Used in This Document . . . . . . . . . . . . . . 3
67 3. Tagged Argument ":fcc" . . . . . . . . . . . . . . . . . . . 3
68 3.1. Interaction with Extensions to the Fileinto Action . . . 3
69 3.1.1. Imap4flags Extension . . . . . . . . . . . . . . . . 4
70 3.1.2. Mailbox Extension . . . . . . . . . . . . . . . . . . 4
71 3.1.3. Special-Use Extension . . . . . . . . . . . . . . . . 4
72 3.2. Collected Grammar . . . . . . . . . . . . . . . . . . . . 5
73 4. Format of FCC Messages . . . . . . . . . . . . . . . . . . . 5
74 5. Interaction with the Vacation Action . . . . . . . . . . . . 6
75 6. Interaction with the Notify Action . . . . . . . . . . . . . 7
76 6.1. Notification-Capability "fcc" . . . . . . . . . . . . . . 7
77 7. Compatibility with the Reject and Extended Reject
78 Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
79 8. Compatibility with Other Actions . . . . . . . . . . . . . . 8
80 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
81 10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9
82 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
83 11.1. Registration of New Sieve Extension . . . . . . . . . . 9
84 11.2. Registration of New Notification-Capability
85 Parameter . . . . . . . . . . . . . . . . . . . . . . . 10
86 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
87 12.1. Normative References . . . . . . . . . . . . . . . . . . 10
88 12.2. Informative References . . . . . . . . . . . . . . . . . 12
89 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12
90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
94 The Sieve email filtering language [RFC5228] provides a number of
95 action commands, some of which can generate additional messages on
96 behalf of the user. It is sometimes desirable for a Sieve user to
97 maintain an archive of the messages generated by these commands.
99 This extension defines ":fcc", a new optional tagged argument for
100 action commands that generate additional messages. This argument
101 allows a copy of the generated message to be filed into a target
104 The capability string associated with this extension is "fcc".
106 Each new action that generates additional messages will need to
107 specify how it interacts with the FCC extension. This document
108 specifies the interaction of the FCC extension with the Vacation
109 [RFC5230] and Notify [RFC5435] actions.
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116RFC 8580 Sieve Extension: FCC May 2019
1192. Conventions Used in This Document
121 Conventions for notations are as described in Section 1.1 of
122 [RFC5228], including use of the "Usage:" label for the definition of
123 the action and the syntax of tagged arguments.
125 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
126 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
127 "OPTIONAL" in this document are to be interpreted as described in
128 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
129 capitals, as shown here.
1313. Tagged Argument ":fcc"
133 This document specifies ":fcc", a new optional tagged argument that
134 alters the behavior of action commands that generate additional
135 messages on behalf of the user.
137 Usage: :fcc <mailbox: string>
139 The ":fcc" tagged argument instructs the Sieve interpreter to file a
140 copy of the generated message into the mailbox provided in the
141 subsequent argument. The semantics and treatment of the mailbox
142 argument are defined to match those of the mailbox argument to the
143 fileinto action specified in Section 4.1 of [RFC5228]. Specifically,
144 use of an invalid mailbox name MAY be treated as an error or result
145 in delivery to an implementation-defined mailbox, and if the
146 specified mailbox doesn't exist, the implementation MAY treat it as
147 an error, create the mailbox, or file the message into an
148 implementation-defined mailbox.
1503.1. Interaction with Extensions to the Fileinto Action
152 Some tagged arguments defined in extensions to the fileinto action
153 can be used together with the ":fcc" tagged argument. The sections
154 below describe these interactions. Tagged arguments in future
155 extensions to the fileinto action need to describe their interaction
156 with the FCC extension, if any.
158 When any fileinto extension arguments are used with the FCC
159 extension, the corresponding extension MUST be enabled, and the
160 arguments are defined to have the same syntax, semantics, and
161 treatment as they do with the fileinto action.
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172RFC 8580 Sieve Extension: FCC May 2019
1753.1.1. Imap4flags Extension
177 This document extends the definition of the ":flags" tagged argument
178 (see Section 5 of [RFC5232]) so that it can optionally be used with
179 the ":fcc" tagged argument.
181 Usage: :fcc <mailbox: string> [:flags <list-of-flags: string-list>]
183 If the optional ":flags" tagged argument is specified with the ":fcc"
184 tagged argument, it instructs the Sieve interpreter to set the IMAP4
185 flags provided in the subsequent argument when the generated message
186 is filed into the target mailbox.
1883.1.2. Mailbox Extension
190 This document extends the definition of the ":create" tagged argument
191 (see Section 3.2 of [RFC5490]) so that it can optionally be used with
192 the ":fcc" tagged argument.
194 Usage: :fcc <mailbox: string> [:create]
196 If the optional ":create" tagged argument is specified with the
197 ":fcc" tagged argument, it instructs the Sieve interpreter to create
198 the target mailbox, if needed, before attempting to file the
199 generated message into the target mailbox.
2013.1.3. Special-Use Extension
203 This document extends the definition of the ":specialuse" tagged
204 argument (see Section 4 of [RFC8579]) so that it can optionally be
205 used with the ":fcc" tagged argument.
207 Usage: :fcc <mailbox: string> [:specialuse <special-use-flag: string>]
209 If the optional ":specialuse" tagged argument is specified with the
210 ":fcc" tagged argument, it instructs the Sieve interpreter to check
211 whether a mailbox exists with the specific special-use flag assigned
212 to it. If such a mailbox exists, the generated message is filed into
213 the special-use mailbox. Otherwise, the generated message is filed
214 into the target mailbox.
216 If the optional ":specialuse" and ":create" tagged arguments are both
217 specified with the ":fcc" tagged argument, the Sieve interpreter is
218 instructed to create the target mailbox per Section 4.1 of [RFC8579],
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2313.2. Collected Grammar
233 For convenience, the "FCC" syntax element is defined here using ABNF
234 [RFC5234] so that it can be augmented by other extensions.
236 Note that the following is the grammar of "FCC" after it has been
237 lexically interpreted. No whitespace or comments appear below.
239 FCC = ":fcc" string *FCC-OPTS
240 ; per Section 2.6.2 of RFC 5228,
241 ; the tagged arguments in FCC may appear in any order
243 FCC-OPTS = CREATE / IMAP-FLAGS / SPECIAL-USE
244 ; each option MUST NOT appear more than once
247 IMAP-FLAGS = ":flags" string-list
248 SPECIAL-USE = ":specialuse" string
2504. Format of FCC Messages
252 Copies of messages filed into a mailbox via this extension are
253 REQUIRED to be in the Internet Message Format [RFC5322]. Some
254 messages generated by Sieve actions might already conform to this
255 format and MAY be filed without modification. Messages generated in
256 other formats MUST be encapsulated using constructs from the Internet
257 Message Format [RFC5322] and MIME ([RFC2045], [RFC2046], [RFC2047],
260 The general requirements for encapsulating the copies of messages to
261 be filed are as follows:
263 o Date: The Date header field is REQUIRED and SHOULD be set to the
264 date and time when the message was generated.
266 o From: The From header field is REQUIRED and SHOULD be set to the
267 email address of the owner of the Sieve script, unless explicitly
268 overridden by rules for encapsulating a particular message type.
270 Per Erratum ID 2035 [Err2035],
272 "Informative advice: Users often have multiple email addresses,
273 and "the email address of the owner of the Sieve script" may
274 offer a choice among several. If the sieve processor
275 recognizes an address belonging to the owner of the Sieve
276 script in the To or Cc fields of the input message, then it's
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284RFC 8580 Sieve Extension: FCC May 2019
287 better to use that address for the From field of the generated
288 message, rather than any other addresses the script's owner may
291 o To: The To header field is OPTIONAL and MAY be set to the email
292 address of the recipient of the generated message, if available.
294 o Subject: The Subject header field is OPTIONAL and MAY be generated
295 by setting the subject to the characters "Fcc: " followed by the
296 subject of the message being processed by the Sieve interpreter.
298 o In-Reply-To: The In-Reply-To header field is OPTIONAL and MAY be
299 set to the Message-ID of the message being processed by the Sieve
302 o Message Body: The body of the filed message is REQUIRED and is
303 composed of one or more MIME parts containing the generated
304 message and any related metadata. The Content-Type header
305 field(s) MUST be set to the appropriate MIME types. If any of the
306 MIME parts include 8-bit or binary data, the Content-Transfer-
307 Encoding header field(s) MUST be set accordingly.
3095. Interaction with the Vacation Action
311 This document extends the Vacation [RFC5230] action (see also
312 "Seconds" parameter [RFC6131] to optionally store a copy of the auto-
313 reply messages into a target mailbox.
315 Usage: vacation [FCC]
316 [":days" number | ":seconds" number]
319 [":addresses" string-list]
324 Example (using fileinto extensions):
326 require ["vacation", "fcc", "mailbox", "special-use", "imap4flags"];
329 :from "hemingway@example.com" "Gone Fishin'"
330 :specialuse "\\Sent" :create
331 :fcc "INBOX.Sent" :flags ["\\Seen"];
333 Vacation auto-reply messages are compliant with MIME and can be filed
334 into the target mailbox without modification.
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3436. Interaction with the Notify Action
345 This document extends the Notify [RFC5435] action to optionally store
346 a copy of the notification messages into a target mailbox.
350 [":importance" <"1" / "2" / "3">]
351 [":options" string-list]
357 require ["enotify", "fcc"];
359 notify :fcc "INBOX.Sent"
360 :message "You got mail!"
361 "mailto:ken@example.com";
363 Messages generated using the "mailto" [RFC5436] notification method
364 are compliant with MIME and can be filed into the target mailbox
365 without modification.
367 Messages generated by other notification methods (e.g., "xmpp"
368 [RFC5437]) MUST be encapsulated per Section 4 before being filed.
369 The body of the filed message MUST include the ":message" tagged
370 argument and MAY include one or more of the ":from", ":importance",
371 or ":options" tagged arguments. The MIME type(s) of the body part(s)
372 used to encapsulate the parameters is an implementation decision.
374 An implementation MAY only support the FCC extension in conjunction
375 with a subset of the notification methods it supports. An error
376 occurs if the FCC extension is used with a notification method that
377 doesn't support it. Notification methods that support the FCC
378 extension can be discovered at runtime using the mechanism described
3816.1. Notification-Capability "fcc"
383 This document defines "fcc", a new notification-capability value for
384 use with the notify_method_capability test (see Section 5 of
385 [RFC5435]. For the "fcc" notification-capability, the
386 notify_method_capability test can match one of the following key-list
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396RFC 8580 Sieve Extension: FCC May 2019
400 A copy of the notification message sent using the method
401 identified by the notification-uri can be filed into a target
405 A copy of the notification message sent using the method
406 identified by the notification-uri cannot be filed into a target
409 Note that the "fcc" notify_method_capability test does not require
410 the notification-uri argument to specify anything other than a
415 require ["enotify", "fcc"];
417 if notify_method_capability "xmpp:" "fcc" "yes" {
418 notify :fcc "INBOX.Sent"
419 :message "You got mail"
420 "xmpp:ken@example.com?message;subject=SIEVE";
422 notify :fcc "INBOX.Sent"
423 :message "You got mail!"
424 "mailto:ken@example.com";
4277. Compatibility with the Reject and Extended Reject Actions
429 Implementations MUST NOT allow use of the FCC extension with the
430 reject and ereject [RFC5429] actions. Allowing use of the FCC
431 extension with these actions would violate the SMTP [RFC5321]
432 principle that a message is either delivered or bounced back to the
433 sender. Namely, the saved copy of the rejection message will contain
434 the original message.
436 It is an error for a script to use the ":fcc" tagged argument with
437 either of the reject or ereject actions.
4398. Compatibility with Other Actions
441 The FCC extension is not compatible with any Sieve action that does
442 not generate an additional message on behalf of the user. It is an
443 error for a script to use the ":fcc" tagged argument with any such
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455 Future extensions that define actions that generate additional
456 messages on behalf of the user need to describe their compatibility
457 with the FCC extension and describe how to MIME-encapsulate the
458 message, if required.
4609. Security Considerations
462 In addition to the security considerations in [RFC5228], [RFC5230],
463 [RFC5435], and [RFC6131], it should be noted that filing copies of
464 generated messages may cause the Sieve script owner to exceed the
465 allocated storage (quota) on the mail system, thereby preventing
466 delivery of future messages destined for the owner.
46810. Privacy Considerations
470 In addition to the privacy considerations in [RFC5228], [RFC5230],
471 [RFC5435], and [RFC6131], it should be noted that a copy of a
472 generated message filed into a shared or public mailbox (as opposed
473 to a private mailbox) could expose private information about the
474 Sieve script owner to third parties. For instance, users that have
475 access to the shared/public mailbox might discover that the Sieve
476 script owner is on holiday or might discover the owner's physical
47911. IANA Considerations
48111.1. Registration of New Sieve Extension
483 IANA has registered the following Sieve extension in the "Sieve
484 Extensions" registry at
485 <https://www.iana.org/assignments/sieve-extensions>:
489 Description: Adds the ":fcc" parameter to Sieve action commands
490 that generate additional messages.
494 Contact address: The Sieve discussion list <sieve@ietf.org>
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51111.2. Registration of New Notification-Capability Parameter
513 IANA has registered the following notification-capability parameter
514 in the "Notification-Capability Parameters" registry at
515 <https://www.iana.org/assignments/notification-capability-
520 Description: Returns whether a copy of the notification message
521 sent using the method identified by the notification-uri parameter
522 to the notify_method_capability test can be filed into a target
525 Syntax: Can contain one of two values: "yes" or "no". Values MUST
530 Contact: The Sieve discussion list <sieve@ietf.org>
53412.1. Normative References
536 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
537 Extensions (MIME) Part One: Format of Internet Message
538 Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
539 <https://www.rfc-editor.org/info/rfc2045>.
541 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
542 Extensions (MIME) Part Two: Media Types", RFC 2046,
543 DOI 10.17487/RFC2046, November 1996,
544 <https://www.rfc-editor.org/info/rfc2046>.
546 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
547 Part Three: Message Header Extensions for Non-ASCII Text",
548 RFC 2047, DOI 10.17487/RFC2047, November 1996,
549 <https://www.rfc-editor.org/info/rfc2047>.
551 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
552 Requirement Levels", BCP 14, RFC 2119,
553 DOI 10.17487/RFC2119, March 1997,
554 <https://www.rfc-editor.org/info/rfc2119>.
562Murchison & Gondwana Standards Track [Page 10]
564RFC 8580 Sieve Extension: FCC May 2019
567 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded
568 Word Extensions: Character Sets, Languages, and
569 Continuations", RFC 2231, DOI 10.17487/RFC2231, November
570 1997, <https://www.rfc-editor.org/info/rfc2231>.
572 [RFC5228] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
573 Filtering Language", RFC 5228, DOI 10.17487/RFC5228,
574 January 2008, <https://www.rfc-editor.org/info/rfc5228>.
576 [RFC5230] Showalter, T. and N. Freed, Ed., "Sieve Email Filtering:
577 Vacation Extension", RFC 5230, DOI 10.17487/RFC5230,
578 January 2008, <https://www.rfc-editor.org/info/rfc5230>.
580 [RFC5232] Melnikov, A., "Sieve Email Filtering: Imap4flags
581 Extension", RFC 5232, DOI 10.17487/RFC5232, January 2008,
582 <https://www.rfc-editor.org/info/rfc5232>.
584 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
585 Specifications: ABNF", STD 68, RFC 5234,
586 DOI 10.17487/RFC5234, January 2008,
587 <https://www.rfc-editor.org/info/rfc5234>.
589 [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
590 DOI 10.17487/RFC5322, October 2008,
591 <https://www.rfc-editor.org/info/rfc5322>.
593 [RFC5429] Stone, A., Ed., "Sieve Email Filtering: Reject and
594 Extended Reject Extensions", RFC 5429,
595 DOI 10.17487/RFC5429, March 2009,
596 <https://www.rfc-editor.org/info/rfc5429>.
598 [RFC5435] Melnikov, A., Ed., Leiba, B., Ed., Segmuller, W., and T.
599 Martin, "Sieve Email Filtering: Extension for
600 Notifications", RFC 5435, DOI 10.17487/RFC5435, January
601 2009, <https://www.rfc-editor.org/info/rfc5435>.
603 [RFC5490] Melnikov, A., "The Sieve Mail-Filtering Language --
604 Extensions for Checking Mailbox Status and Accessing
605 Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March
606 2009, <https://www.rfc-editor.org/info/rfc5490>.
608 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
609 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
610 May 2017, <https://www.rfc-editor.org/info/rfc8174>.
612 [RFC8579] Bosch, S., "Sieve Email Filtering: Delivering to Special-
613 Use Mailboxes", RFC 8579, DOI 10.17487/RFC8579, May 2019,
614 <https://www.rfc-editor.org/info/rfc8579>.
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62312.2. Informative References
625 [Err2035] RFC Errata, Errata ID 2035, RFC 5230,
626 <https://www.rfc-editor.org/errata_search.php?eid=2035>.
628 [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
629 DOI 10.17487/RFC5321, October 2008,
630 <https://www.rfc-editor.org/info/rfc5321>.
632 [RFC5436] Leiba, B. and M. Haardt, "Sieve Notification Mechanism:
633 mailto", RFC 5436, DOI 10.17487/RFC5436, January 2009,
634 <https://www.rfc-editor.org/info/rfc5436>.
636 [RFC5437] Saint-Andre, P. and A. Melnikov, "Sieve Notification
637 Mechanism: Extensible Messaging and Presence Protocol
638 (XMPP)", RFC 5437, DOI 10.17487/RFC5437, January 2009,
639 <https://www.rfc-editor.org/info/rfc5437>.
641 [RFC6131] George, R. and B. Leiba, "Sieve Vacation Extension:
642 "Seconds" Parameter", RFC 6131, DOI 10.17487/RFC6131, July
643 2011, <https://www.rfc-editor.org/info/rfc6131>.
647 The authors would like to thank the following individuals for
648 contributing their ideas and supporting this specification: Ned
649 Freed, Stan Kalisch, and Alexey Melnikov.
655 1429 Walnut Street, Suite 1201
656 Philadelphia, PA 19102
657 United States of America
659 Email: murch@fastmailteam.com
664 Level 2, 114 William Street
668 Email: brong@fastmailteam.com
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