End-to-end RFC 3798 Message Disposition Notification support, covering
both sides of the receipt flow — requesting a receipt when composing, and
responding to one (send or decline) when reading.
Request side (compose)
- New --request-receipt flag on +send / +reply / +reply-all / +forward /
+draft-create / +draft-edit. When set, the outgoing EML carries a
Disposition-Notification-To header (RFC 3798) addressed to the resolved
sender. Recipient mail clients may prompt the user, auto-send a receipt,
or silently ignore — delivery is not guaranteed.
- requireSenderForRequestReceipt gates the flag against a controlled
sender address resolved BEFORE the orig.headTo fallback in +reply /
+reply-all / +forward, so the DNT cannot silently land on someone else
in CC / shared-mailbox flows.
Response side
- +send-receipt: build a system-templated reply for messages carrying the
READ_RECEIPT_REQUEST label (-607). Subject / recipient / sent / read
time layout matches the Lark client; body is non-customizable — receipt
bodies are system templates by industry convention; free-form notes
belong in +reply. Risk:"high-risk-write" + --yes required.
- +decline-receipt: clear READ_RECEIPT_REQUEST without sending anything
(mirrors the client's "不发送" / "Don't send" button). Idempotent on
re-run; Risk:"write" — no --yes needed.
Read-path hints
- +message / +messages / +thread emit a stderr hint when surfacing a
mail carrying READ_RECEIPT_REQUEST, exposing BOTH response paths
(+send-receipt --yes / +decline-receipt) so agents present a real
choice to the user instead of silently auto-sending.
Guard rails
- +send / +reply / +reply-all / +forward stay draft-by-default and
require --confirm-send to send, gated by a dynamic scope check for
mail:user_mailbox.message:send (absent from the default scope set so
draft-only flows don't need the sensitive permission).
- All header-bound user input (sender / display name / recipient /
subject) goes through CR/LF rejection plus Bidi / zero-width / line-
separator guards, mirroring emlbuilder.validateHeaderValue, to block
header injection and visual spoofing.
- Hint output strips terminal control characters (CR, LF) from any
untrusted field embedded into the user-visible suggestion.
Backend coupling
- Outgoing receipt EML carries the private header
X-Lark-Read-Receipt-Mail: 1. The data-access backend parses it into
BodyExtra.IsReadReceiptMail; DraftSend then applies READ_RECEIPT_SENT
(-608) and clears READ_RECEIPT_REQUEST (-607) from the original
message, closing the client-side banner.
- en receipts require backend TCC SubjectPrefixListForAdvancedSearch to
include "Read Receipt:" for conversation-view aggregation; zh prefix
("已读回执：") is already configured.
Docs: new reference pages for +send-receipt / +decline-receipt;
--request-receipt noted on each compose-side reference; SKILL.md
workflow (section 9) describes the full privacy-safe decision tree on
both sides.
Tests cover emlbuilder DispositionNotificationTo / IsReadReceiptMail
helpers, receiptMetaLabels (zh / en), buildReceiptSubject, text and HTML
body generators (with HTML escaping and Bidi guards), header-injection
defenses, sender-resolution gating (CC-only / shared-mailbox regression),
hint emission paths, and the full +send-receipt / +decline-receipt happy
+ idempotent paths via httpmock.
