native/docs/parity/03-email-viewer.md

Email viewer / thread view / message rendering / attachments

Summary

RN has a solid single-message reader (WebView body with CSP, shrink-to-fit + pinch zoom, external-content gate with trusted senders, cid inlining, attachment open/share/save with templated filenames, view source, .eml export, calendar-invitation banner, shared-folder routing for body/attachments/source) but it is a single-message viewer, not a thread view, and it never fetches headers/messageId/inReplyTo/references, so everything the WEB viewer derives from headers (SPF/DKIM/DMARC, List-Unsubscribe, read receipts, Reply-To, identity badge, correct In-Reply-To) is absent or wrong. The biggest gaps: (1) older messages of a thread are unreachable and the pager shows the wrong message when opened from the unified inbox / contact activity; (2) replies write the JMAP id into In-Reply-To, ignore Reply-To, do not strip the user's own address on reply-all, and forwards drop every attachment; (3) HTML-only messages (same part in textBody and htmlBody) are rendered and quoted as raw HTML source, and <style> blocks are stripped wholesale, which is the most likely root of native issues #46 ("email preview shows css") and #49 ("Unreadable text in dark-mode emails"); (4) external-content blocking only recognises <img src=http…>, background= and inline url(), so srcset/<source>/poster/whitespace-obfuscated pixels still load.

Findings

Thread view / navigation

• Thread messages other than the newest are unreachable — fixed in d2ed27f — P1 — missing

  • What WEB does: opening a thread renders every message of the thread as expandable cards (newest + all unread auto-expanded), each with its own body, attachments, reply/forward and mark-read-on-expand (components/email/thread-conversation-view.tsx:98-115, 171-200, store fetchThreadEmails via Thread/get + Email/get in stores/email-store.ts:3574-3640, lib/jmap/client.ts:2763-2800).
  • What RN does: the list collapses same-thread rows to the newest message with a count badge (src/screens/EmailListScreen.tsx:224-238, default disableThreading: false at src/stores/settings-store.ts:266), the row opens EmailThreadScreen with a single emailId (App.tsx:145-151), and the screen only ever shows that one message (src/screens/EmailThreadScreen.tsx:113-120, 685-840). getThread exists in src/api/email.ts:448 but is only used by a test. Older messages of a thread cannot be opened at all unless the user turns on "Disable Thread Grouping".
  • Fix hint: on open, call getThread(threadId, ownerAccountId) + getFullEmails(ids) and render a vertical list of collapsible message cards inside the pane (newest + unread expanded), reusing EmailBodyView per card; keep the horizontal pager for thread-to-thread navigation.

• Pager shows the wrong message (or nothing) when the opened email is not in the store list — fixed in c8be383 — P1 — rn-only-bug — the body was right after c8be383, but delete, archive, move and spam hit the open folder's account, and new mail moved the page, until 5c7301b and 9c31de2 (audit B3, B5)

  • What WEB does: the viewer renders selectedEmail directly; prev/next are derived from the current list (components/email/email-viewer.tsx:5220-5279).
  • What RN does: the pager is a FlatList over useEmailStore(s => s.emails) and the initial index is Math.max(0, emails.findIndex(id)) (src/screens/EmailThreadScreen.tsx:128-133, 535-572). UnifiedInboxScreen keeps its own local list and never writes the store (src/screens/UnifiedInboxScreen.tsx:35-50, 61-84), ContactActivity navigates with ids from a contact search (src/components/contacts/ContactActivity.tsx:170-177). In both cases the opened id is absent from emails, so the visible pane is emails[0] (a different mailbox's first message, or blank when the list is empty) while the toolbar/mark-read/delete act on activeEmailId.
  • Fix hint: when route.params.emailId is not in emails, render a single-item pager (data=[{id: emailId}]) and disable prev/next; or have the unified inbox / contact activity pass their own id list through route params.

• Mark-as-read "Never" (-1) marks the message read instantly — fixed in d2ed27f — P2 — rn-only-bug

  • What WEB does: -1 means never auto-mark, 0 instant, >0 delayed (components/email/email-viewer.tsx:1218-1238).
  • What RN does: ReadingSettings offers Never = -1 (src/components/settings/ReadingSettings.tsx:167-173) but the viewer does if (markAsReadDelay > 0) {timer} else { markRead() } (src/screens/EmailThreadScreen.tsx:237-245), so -1 behaves like instant.
  • Fix hint: add if (markAsReadDelay === -1) return; before the branch.

• Skeleton / loading parity — verified, no action — P3 — verified (see "Verified at parity"); no action.

Body rendering & sanitisation

• HTML-only messages are rendered (and quoted) as raw HTML source — native issue #46 "email preview shows css" — fixed in 06742ef — P1 — bug

  • What WEB does: per RFC 8621 §4.1.4 an HTML-only message exposes the same part in textBody and htmlBody; WEB checks hasDistinctTextBody (different partIds) before preferring the text alternative, and routes by the part's type (components/email/email-viewer.tsx:1727-1747, components/email/thread-conversation-view.tsx:332-346; changelog 1.6.3 "Render HTML-only emails", "Render plain-text-only emails as text, not HTML").
  • What RN does: extractTextBody returns the html part's value for HTML-only mail, then rawHtml = html && (!text || hasMeaningfulHtmlBody(html)) ? html : null (src/components/EmailBodyView.tsx:43-57, 504-511). For any HTML-only message whose markup fails MEANINGFUL_HTML_RE (src/lib/email-html.ts:353-362, e.g. a <div>/<p> body without style=), rawHtml is null and the raw source — tags, <head>, CSS — is shown as plain text. The same value feeds the reply quote: plainTextBody() (src/screens/EmailThreadScreen.tsx:59-65, 377) so replies to HTML-only mail quote escaped HTML source.
  • Fix hint: compare textBody[0].partId !== htmlBody[0].partId (and part.type === 'text/html') before treating text as an alternative; in navigateCompose pass htmlBody (and let buildInitialHtml use it) or convert with htmlToPlainText (src/lib/compose-html.ts:108) when the only body is HTML.

• <style> blocks are stripped from every HTML email — layout/colour loss, likely native issue #49 "Unreadable text in dark-mode emails" — fixed in 06742ef — P2 — bugfix-parity

  • What WEB does: iframe sanitiser keeps <style> (lib/email-sanitization.ts:60-78), and when external content is blocked it neutralises url()/@import/@font-face inside the sheet (stripExternalStyleSheetCss, lib/email-sanitization.ts:474-509, changelog 1.7.8 #457) while the strict iframe CSP is the network backstop (components/email/email-viewer.tsx:2265-2267).
  • What RN does: FORBID_TAGS includes 'style' (and svg) so every stylesheet is removed before render (src/lib/email-html.ts:16-28, 50-68). Class-based colours vanish: a newsletter with white text via .hero { color:#fff } on a bgcolor cell renders white-on-white (light) or, after the invert filter, black-on-black. Also hasNativeDarkMode is evaluated on the stripped HTML inside wrapEmailHtml (src/lib/email-html.ts:226-229) but on the raw HTML in the component (src/components/EmailBodyView.tsx:612-613), so for emails with @media (prefers-color-scheme: dark) the CSS inversion is applied but the DOM re-invert pass is skipped.
  • Fix hint: keep <style> (the WebView is an isolated document; CSP already has style-src 'unsafe-inline'), port stripExternalStyleSheetCss + decodeCssEscapes for the blocked case, and evaluate hasNativeDarkMode once on the same input.

• Dark-mode inversion CSS is an older revision of WEB's — fixed in d2ed27f — P2 — bugfix-parity

  • What WEB does (1.7.4 "Correct dark-mode background-image inversion and height clipping", 1.6.3 emoji/nested bgcolor, 1.7.7 height:100% wrappers): background-image containers are re-inverted unconditionally and their media get filter:none; only bgcolor/background: containers use the :not(:has(media)) guard; nested guard is limited to colour containers; [style*="height:100%"] is neutralised; Word/Outlook HTML gets line-height:1.15 + MsoNormal margins and a fallback gutter; messageSpacing auto/edge gutter (components/email/email-viewer.tsx:2200-2253, 2287-2305, 2438-2461).
  • What RN does: DARK_INVERSION applies the :not(:has(...)) guard to background-image containers too and includes them in the nested filter:none rule (src/lib/email-html.ts:167-185), the DOM pass only re-inverts containers without media children (src/components/EmailBodyView.tsx:72-88); no Word/Outlook padding, no per-message light/dark toggle (WEB toolbar Sun/Moon, email-viewer.tsx:3199-3212, changelog 1.6.0), no messageSpacing.
  • Fix hint: copy the current darkModeCSS block and the DOM re-invert loop verbatim into email-html.ts / DARK_REINVERT_SCRIPT; add a "View in light/dark mode" entry to the More sheet that overrides renderAsDark for the current message.

• External-content detection misses most tracking vectors (privacy leak) — fixed in 06742ef — P2 — bugfix-parity

  • What WEB does: isExternalResourceUrl strips C0/space so "\nhttps://x" and h\ttps:// count; blocks <img srcset>, <picture><source>, <video poster>, media src, background=, inline url() incl. CSS escapes, <style> url()/@import, and forbids <link> in blocking mode; the banner is driven by "something was actually blocked" (lib/email-sanitization.ts:399-406, 511-615, 108-150; changelog 1.7.8).
  • What RN does: hasRemoteContent only matches <img src="http…">, background="http…" and style="...url(http…)" (src/lib/email-html.ts:364-369); when it returns false shouldBlock is false and the CSP becomes img-src data: cid: https: http: (src/lib/email-html.ts:235), so a pixel expressed as srcset=, <source>, poster=, src=" https://…" (leading whitespace/newline), or a CSS-escaped \68ttps:// loads unconditionally under policy ask/block. blockRemoteImageSrcs (316-347) is likewise src/srcset/background/style only, and has no data-blocked-* restore.
  • Fix hint: make the gate policy-driven rather than detection-driven (block = strict CSP img-src data: cid: + media-src/font-src none whenever policy is block/ask-not-allowed and sender untrusted, like WEB's externalBlocked), port isExternalResourceUrl normalisation, add source/video/audio/poster/link handling, and show the banner when the strict CSP is in effect and the HTML contains any http(s):// resource reference.

• Blocked images leave broken-image icons / alt text; empty containers not collapsed — fixed in 06742ef — P3 — bugfix-parity

  • What WEB does: swaps src for a transparent 1x1 GIF, empties alt, display:none, and collapses empty <td>/<div> wrappers (lib/email-sanitization.ts:319-320, 537-546, 678-704); hides images that fail to load (components/email/email-viewer.tsx:2393-2411, changelog 1.7.7).
  • What RN does: sets src="" and alt="[remote image blocked]" (src/lib/email-html.ts:319-323), so blocked newsletters show rows of broken-image glyphs with English alt text; no failed-image hiding.
  • Fix hint: use the same transparent-GIF + display:none swap and port collapseBlockedImageContainers as a regex/DOM pass in the injected script; add an img error listener that hides the element.

• mailto: links inside the body open the OS mail handler instead of the app composer — fixed in 06742ef — P2 — missing

  • What WEB does: mailto: opens the built-in composer with parsed to/subject/body (changelog 1.8.1 "Open mailto: links in the built-in composer"; iframe click handler leaves mailto: to the app's protocol handling, components/email/email-viewer.tsx:2420-2436).
  • What RN does: onShouldStartLoadWithRequest hands mailto: to Linking.openURL (src/components/EmailBodyView.tsx:715-724), so tapping an address in an email opens Gmail/Apple Mail instead of Bulwark.
  • Fix hint: parse mailto: (address, subject, body, cc) and navigation.navigate('Compose', { prefillTo, ... }); the prefillTo param already exists (src/screens/ComposeScreen.tsx:292-298).

• data: URL navigations replace the email body — fixed in 06742ef — P3 — rn-only-bug

  • What RN does: onShouldStartLoadWithRequest returns true for any data: URL (src/components/EmailBodyView.tsx:717-719), and safeUri keeps href="data:image/…" (src/lib/email-html.ts:109-113); tapping such a link navigates the WebView to the image with no way back. Only the initial about:blank load should be allowed.
  • Fix hint: allow data: only when request.navigationType === 'other' && !request.isTopFrame-style initial loads, otherwise return false (optionally open images externally).

• Regex sanitiser + script-src 'unsafe-inline': keep the data-URI/SVG allowlist in sync with WEB — fixed in 06742ef — P3 — partial

  • What WEB does: allows only raster data:image/(png|jpe?g|gif|webp|bmp|avif|x-icon|vnd.microsoft.icon) on media tags, re-checks srcset candidates individually, forbids SVG data URIs and <svg> (lib/email-sanitization.ts:24, 330-388), and the iframe has no scripting at all.
  • What RN does: safeUri allows any data:image/* including image/svg+xml (src/lib/email-html.ts:109-113), srcset values are never scheme-checked except when blocking (326-329), and the page CSP must allow 'unsafe-inline' scripts for the injected bridge (236-245), so a parser-differential bypass of the regex stripper would execute script in the WebView (limited blast radius: the bridge only accepts height/swipe/zoom strings).
  • Fix hint: restrict data: to the raster list, scheme-check every srcset candidate, and consider parsing with a real HTML parser (e.g. htmlparser2/parse5 on the JS side) instead of regexes; document the residual risk.

• Quoted reply text is not collapsed (#480) — fixed in 06742ef — P3 — missing

  • What WEB does: hides the trailing quote (Gmail/Outlook/Apple/Thunderbird/Bulwark markers, attributed <blockquote>, >-lines in plain text) behind a "•••" toggle (lib/quote-collapse.ts:143-197, 219-259; changelog 1.7.8).
  • What RN does: nothing; long threads show every quoted original inline.
  • Fix hint: port setupQuoteCollapse into the injected WebView script (runs on the parsed DOM, uses inline styles only) and collapsePlainTextQuotes into wrapPlainTextEmail.

• Plain-text bodies are always monospace (#830) — fixed in 06742ef — P3 — bugfix-parity

  • What WEB does: renders text/plain in the app font by default with a plainTextFont: 'sans' | 'mono' setting (stores/settings-store.ts:329, 565; components/email/email-viewer.tsx:5050-5060; changelog 1.9.0).
  • What RN does: wrapPlainTextEmail hard-codes ui-monospace, Menlo, … (src/lib/email-html.ts:290); no setting (src/stores/settings-store.ts has no plainTextFont).
  • Fix hint: add the setting (Reading settings) and switch the font-family in wrapPlainTextEmail.

• Plain-text linkifier only catches http(s) — verified, no action — P3 — verified (same as WEB plainTextToSafeHtml); no action.

• cid images larger than 2 MB and non-image cid parts silently show a 1x1 placeholder; octet-stream cid parts (#543) unverified — fixed in 06742ef — P3 — partial

  • What WEB does: fetches every cid part as an authenticated blob: URL regardless of size/type; the browser sniffs application/octet-stream image bytes (components/email/email-viewer.tsx:1509-1575; changelog 1.8.1 #543).
  • What RN does: skips parts over MAX_INLINE_IMAGE_BYTES (src/components/EmailBodyView.tsx:15, 556-559) and builds data:${att.type || 'application/octet-stream'};base64,… (573), which Chromium/WebKit may refuse to decode as an image for application/octet-stream.
  • Fix hint: sniff magic bytes (PNG/JPEG/GIF/WebP) to pick the MIME for the data URI; for >2 MB parts encode off the JS thread (e.g. File.base64() from expo-file-system after downloadInto) instead of dropping them.

Header / meta

• headers, messageId, inReplyTo, references are never fetched — fixed in ccbe67c — P2 — missing (root cause for the next five items)

  • What WEB does: Email/get requests messageId, inReplyTo, references, headers, bodyStructure and parses Authentication-Results, X-Spam-*, X-Spam-LLM into email.authenticationResults/spamScore/spamLLM (lib/jmap/client.ts:1775-1870).
  • What RN does: EMAIL_FULL_PROPERTIES stops at bodyStructure, textBody, htmlBody, bodyValues, attachments, blobId, bcc, replyTo, sentAt (src/api/email.ts:11-15); the Email type has no headers/messageId (src/api/types.ts:65-87).
  • Fix hint: add the four properties to EMAIL_FULL_PROPERTIES, extend the type, and port parseAuthenticationResults/parseSpamScore/extractListHeaders (lib/email-headers.ts) to src/lib/email-headers.ts.

• No "Show details" panel: CC/BCC/Reply-To/sent vs received/size/MIME/Message-ID/thread id — fixed in d2ed27f — P2 — missing

  • What WEB does: header shows To/CC/BCC (first 2 + "+N", "me" substitution), a "Show details" toggle with recipients & routing, delivery delta, identifiers/threading, message properties, mailing-list section (components/email/email-viewer.tsx:3892-3944, 4187-4542).
  • What RN does: one line to <names> (src/screens/EmailThreadScreen.tsx:806-809); CC/BCC/Reply-To are fetched but never shown; date/size only (811-817).
  • Fix hint: add CC/BCC rows and a collapsible details block under the sender row; reuse formatSize.

• SPF/DKIM/DMARC/spam-score chips and spoof-aware identity badge — fixed in d2ed27f — P3 — missing

  • What WEB does: auth chips with severity-ranked SPF (HELO vs MAIL FROM, #650), DMARC policy, iprev, spam score/LLM verdict (components/email/email-viewer.tsx:4353-4438, lib/email-headers.ts:13-115); "via " / sub-address tag badge hidden when spoofed (components/email/email-identity-badge.tsx:33-68, changelog 1.7.3).
  • What RN does: none.
  • Fix hint: after the headers finding, render chips in the details block; port isAuthenticationSpoofed for the badge.

• List-Unsubscribe (RFC 2369) banner — fixed in d2ed27f — P2 — missing

  • What WEB does: parses List-Unsubscribe (http preferred, else mailto), confirm dialog, sends the mailto unsubscribe through the account itself, remembers dismissals per Message-ID (components/email/unsubscribe-banner.tsx:64-106, components/email/email-viewer.tsx:753-773, 2672-2680; changelog 1.7.7).
  • What RN does: none.
  • Fix hint: port parseUnsubscribeUrls/isValidUnsubscribeUrl from lib/validation.ts; for mailto call sendEmail with the parsed fields; open http via expo-web-browser.

• Read receipts (MDN, RFC 8098): request banner, send, "always/ask/never", $mdnsent — fixed in d2ed27f — P2 — missing — the receipt headers were not sanitized (GHSA-w38p) and "Always send" answered the unseen neighbour pages until cb6ddd6 and 5f3f584 (audit S1, B7)

  • What WEB does: detects Disposition-Notification-To, offers Send/Ignore (or auto-sends in "always" mode) only in received folders, builds the multipart/report with lib/mdn.ts, uploads → Email/import into Sent → EmailSubmission/set with explicit envelope, then sets $mdnsent (components/email/email-viewer.tsx:2686-2784, lib/jmap/client.ts:4080-4130, components/email/read-receipt-banner.tsx).
  • What RN does: none; no readReceiptResponse setting.
  • Fix hint: port lib/mdn.ts verbatim (pure string builder), reuse uploadBytes (src/api/blob.ts:67) + importEmailBlob (src/api/email.ts:423) + an EmailSubmission/set helper; add the setting.

• Reply-To shown / used — fixed in 7f956d6 — folded into the reply-recipients finding below.

• Sender / recipient tap actions (popover, view/add contact, copy address) — fixed in d2ed27f — P3 — missing

  • What WEB does: every address is a RecipientPopover (contact lookup, extra emails/phones, copy, email, view/add contact); tapping the avatar opens the contact sidebar or, on mobile, the contact page (components/email/recipient-popover.tsx, components/email/email-viewer.tsx:1140-1170, 3841-3866).
  • What RN does: names are static Text (src/screens/EmailThreadScreen.tsx:794-810).
  • Fix hint: wrap sender/recipients in Pressable opening a small action sheet (copy, compose to, open ContactDetail/ContactForm prefilled).

• Displayed date uses receivedAt and device locale, ignoring the app's time-format setting — fixed in d2ed27f — P3 — bugfix-parity

  • What WEB does: emailDisplayDate prefers sentAt (falls back when missing or >24 h in the future, #891) and formats with the user's timeFormat/locale (lib/email-date.ts:33-45, components/email/email-viewer.tsx:3811).
  • What RN does: formatHeaderDate(email.receivedAt) with toLocaleDateString(undefined, …) (src/screens/EmailThreadScreen.tsx:39-50, 812-816), so imported/migrated mail shows the import date and 12/24 h ignores the setting.
  • Fix hint: port emailDisplayDate (already in src/lib/date-format.ts?—if not, 15 lines) and use useSettingsStore(s => s.timeFormat) + locale from useLocaleStore.

• Tags, $important badge and answered/forwarded state in the header — fixed in d2ed27f — P3 — missing

  • What WEB does: tag badges (removable) under the subject, "Important" pill (components/email/email-viewer.tsx:3789-3806); $answered/$forwarded set after send (components/mail/mail-app.tsx:1663-1667).
  • What RN does: Tag sheet exists but no badges are rendered in the pane; $answered/$forwarded are never set after a reply/forward (no hit for $answered in src/).
  • Fix hint: render keywordDefs matches from email.keywords under the subject; after a successful send in ComposeScreen call setEmailKeywords(originalId, {...keywords, $answered|$forwarded: true}, accountId). (setEmailKeywords is gone since 5041897: set keywords/$answered or keywords/$forwarded through patchKeywordsForEmails or the store's setKeywordForEmails.)

Calendar invitation banner

• Invitation parsing is not routed to the owning account (#847, #867) — fixed in 8206893 — P2 — bugfix-parity

  • What WEB does: parses/fetches the ICS through the message's source client and owner account, including directly viewed shared folders (components/email/calendar-invitation-banner.tsx:373-388, 412-432; changelog 1.9.0).
  • What RN does: parseCalendarBlob(attachment.blobId) uses jmapClient.accountId (src/components/email/CalendarInvitationBanner.tsx:54, src/api/calendar.ts:355-360) even though EmailPane knows jmapAccountId; Stalwart answers CalendarEvent/parse with an error for a blob in another account, so invitations in group/shared mailboxes show nothing (state error → banner hidden).
  • Fix hint: pass jmapAccountId from EmailPane into the banner and through to parseCalendarBlob(blobId, accountId).

• iMIP method detection ignores the raw ICS METHOD and Content-Type params — fixed in 8206893 — P2 — partial

  • What WEB does: reads method= from the part/attachment/header Content-Type, then fetches the raw ICS and reads METHOD: (lib/calendar-invitation.ts:319-339, components/email/calendar-invitation-banner.tsx:419-447), falling back to participant heuristics; CANCEL, REPLY, COUNTER, REFRESH, DECLINECOUNTER, PUBLISH, ADD each get their own title/info/actions.
  • What RN does: extractMethodFromRawIcs exists (src/lib/calendar-invitation.ts:103-106) but is never called; only inferInvitationMethod heuristics are used (CalendarInvitationBanner.tsx:62), so a cancellation whose event status is not cancelled, or a REPLY from a single attendee, is shown as a plain invitation with RSVP buttons.
  • Fix hint: fetch the blob text (getDownloadUrl + secureFetch, as fetchRawEmail does) in parallel with parse and prefer extractMethodFromRawIcs.

• Banner lacks WEB's trust assessment, actor summary, existing-event / "already in calendar" state, calendar picker, "View in calendar", collapse, sequence badge, counter-proposal review — P3 — partial — deferred: trust assessment, iTIP method and calendar picker landed in 8206893 (calendar agent); the existing-event state followed in c0582ab, which looks the event up on the server by uid (also so Accept sends the RSVP, audit B22); "View in calendar", collapse, sequence badge and counter-proposal review remain open in the calendar area

  • What WEB does: getInvitationTrustAssessment (sender vs organizer + auth results) warning, actor line ("X accepted"), queryCalendarEvents({uid}) to show "already in calendar" and current RSVP, picker when >1 calendar, "View in calendar" navigation, collapsible card, sequence "updated" pill, apply counter proposal for organizers (components/email/calendar-invitation-banner.tsx:392-474, 502-553, 657-672, 721-752, 802-1140).
  • What RN does: title/date/location/video/organizer rows, Yes/Maybe/No, Add to first writable calendar (src/components/email/CalendarInvitationBanner.tsx:83-207); no dedupe check before offering "Add", no picker, no trust warning, no navigation to the event.
  • Fix hint: port getInvitationTrustAssessment (needs the headers finding for auth), look up useCalendarStore.events by uid to switch to "already in calendar"/current response, add a calendar picker sheet when calendars.length > 1, and a "View in calendar" button that navigates to CalendarScreen with the start date.

• The .ics part stays in the attachment list while the banner is shown — fixed in d2ed27f — P3 — bugfix-parity

  • What WEB does: hides calendar MIME parts when the banner renders (components/email/email-viewer.tsx:1591-1600; changelog 1.4.14).
  • What RN does: renderAttachments filters only inline images (src/screens/EmailThreadScreen.tsx:713-722).
  • Fix hint: filter isCalendarType(att.type) || name.endsWith('.ics') when calendarInvitationParsingEnabled && findCalendarAttachment(email).

Attachments

• Forwarding drops every attachment — fixed in 7f956d6 — P1 — bug

  • What WEB does: forward pre-populates the composer with the original's attachments by blobId (minus embedded cid images) (components/email/email-composer.tsx:598-616, #543).
  • What RN does: navigateCompose('forward') passes only from/to/cc/subject/plain body (src/screens/EmailThreadScreen.tsx:366-382); the Compose.replyTo param has no attachments field (src/navigation/types.ts:7-19) and ComposeScreen never seeds attachments from the original (src/screens/ComposeScreen.tsx:354). A forwarded invoice arrives without the PDF.
  • Fix hint: add attachments?: Attachment[] to the route param, and in ComposeScreen initialise attachments with {blobId,name,type,size} entries (blobs are account-scoped so no re-upload is needed; for shared-folder messages the blob belongs to the owner account — either re-upload via getDownloadUrl(..., ownerAccountId) + uploadBytes, or block forward there).

• message/rfc822 attachments: no inline unwrap, no .eml preview — fixed in d2ed27f — P2 — missing

  • What WEB does: when the outer body is empty (Outlook "forward as attachment") it parses the embedded message with postal-mime and renders its body + attachments, keeping the .eml chip; .eml attachments preview like an email (components/email/email-viewer.tsx:1433-1507, 1625-1636; changelog 1.7.3, 1.8.1).
  • What RN does: the message renders "(empty message)" and the .eml chip can only be shared.
  • Fix hint: add postal-mime (pure JS, works in RN with a TextDecoder polyfill) and mirror the unwrap effect; render the parsed HTML through EmailBodyView.

• TNEF winmail.dat is not decoded — fixed in d2ed27f — P3 — missing

  • What WEB does: parses winmail.dat (body + embedded attachments) and hides the container (lib/tnef.ts, components/email/email-viewer.tsx:1344-1431).
  • What RN does: shows winmail.dat as an opaque attachment; the real files inside are unreachable.
  • Fix hint: lib/tnef.ts is pure Uint8Array code; copy it and feed jmapClient.fetchBlobArrayBuffer.

• Attachment chip list: no MIME-based fallback names, MDN/DSN report parts and non-inline cid images mishandled — fixed in d2ed27f — P3 — partial — body-embedded cid: parts typed octet-stream are hidden from the chips since 1d1d6a5

  • What WEB does: unnamed parts get Document.pdf/Email.eml/Attachment.<sub> (components/email/email-viewer.tsx:191-225); message/disposition-notification and message/delivery-status parts are hidden (1604-1606); inline hiding requires disposition === 'inline' (1601-1603).
  • What RN does: unnamed → 'attachment' (src/screens/EmailThreadScreen.tsx:745); report parts are listed; any cid image is hidden regardless of disposition (719-721), so an image attached with a Content-ID but disposition: attachment (common from some clients) disappears from the list even when the body does not reference it.
  • Fix hint: port getAttachmentDisplayName, add the two report-type filters, and check disposition === 'inline' (or that the body actually references the cid via extractCidRefs).

• No image thumbnails on chips, no "Download all" zip, no per-chip Preview vs Download choice — fixed in d2ed27f — P3 — missing

  • What WEB does: image chips show the actual image (≤10 MB), a "Download all" bundles into a zip named by template, hover reveals separate Download/Preview buttons (components/email/email-viewer.tsx:2024-2102, 2104-2161, 3949-4085; changelog 1.6.0, 1.7.5).
  • What RN does: single tap follows the global mailAttachmentAction; jszip is already a dependency (package.json:36) but unused for mail.
  • Fix hint: long-press sheet with "Open / Save / Share"; a "Download all" entry building the zip with jszip into Paths.cache then sharing.

• In-app attachment preview (images, PDF, text, audio/video) is absent; iOS "Preview" is just the share sheet — fixed in d2ed27f; audio/video, HTML, Markdown, SVG, Android PDFs and ZIPs since 0.1.80-0.1.82 — P3 — partial

  • What WEB does: FilePreviewModal for images/PDF (bytes handed to pdf.js, #871)/text/markdown/audio/video/eml, script-bearing types forced to download (components/mail/mail-app.tsx:2887-2935, lib/file-preview.ts:29-92).
  • What RN does: Android hands the file to an external viewer via ACTION_VIEW, iOS opens the share sheet (src/lib/email-export.ts:64-79, 115-141); nothing is previewed inside the app.
  • Fix hint: for images/PDF/text open a modal WebView on the cached file:// (or use expo-file-system's File.uri with a QuickLook bridge on iOS); keep the external-viewer path as fallback.

• Post-export action (archive/trash after "Export .eml") missing — fixed in d2ed27f — P3 — missing

  • What WEB does: postExportAction setting runs archive/trash after export (components/email/email-viewer.tsx:2559-2571).
  • What RN does: export only (src/screens/EmailThreadScreen.tsx:632-640).
  • Fix hint: add the setting and call onArchive/onDelete after shareEmailEml resolves.

Actions from the viewer

• In-Reply-To/References are written with the JMAP email id (#234 bugfix-parity) — fixed in 7f956d6 — P1 — bug

  • What WEB does: passes the original's RFC messageId and references, stripped of brackets, as JMAP inReplyTo/references arrays (lib/jmap/client.ts:3124-3194; changelog 1.5.4 #234).
  • What RN does: navigateCompose sets inReplyTo: email.id (src/screens/EmailThreadScreen.tsx:379), and sendEmail writes it verbatim into header:In-Reply-To:asText / header:References:asText (src/api/email.ts:823-826). The outgoing header is a bare Stalwart object id, not a msg-id, so recipients' clients cannot thread the reply and References is never accumulated. messageId/references are not even fetched (see headers finding).
  • Fix hint: fetch messageId/references, pass inReplyTo: email.messageId?.[0] and references: [...(email.references ?? []), email.messageId[0]], and send them as JMAP inReplyTo/references arrays (or <…>-wrapped header:…:asMessageIds).

• Reply addressing: Reply-To ignored, own addresses kept on reply-all, self-sent thread replies (#703), external Reply-To on self-sent (1.9.0) — fixed in 7f956d6 — P1 — bugfix-parity

  • What WEB does: buildReplyRecipients — reply goes to Reply-To if present else From; reply-all adds original To/CC minus the user's own identities (exact and +tag-stripped); replying to your own message continues to its original recipients; an external Reply-To on a self-sent message still wins (lib/reply-recipients.ts:74-111, components/mail/mail-app.tsx:920, 2940-2944).
  • What RN does: initialTo = From (+ all original To on reply-all, including the user's own address), initialCc = all CC; email.replyTo is fetched but never passed (src/screens/ComposeScreen.tsx:299-319, src/screens/EmailThreadScreen.tsx:366-382). Replying to a newsletter with Reply-To: support@… mails the no-reply sender; reply-all sends the user a copy; replying to your own sent message addresses yourself.
  • Fix hint: copy lib/reply-recipients.ts (pure), pass replyToAddresses: email.replyTo in the route param and the identities' emails as ownEmails.

• Reply/forward quote is plain text only — HTML formatting and inline images lost (#163, #543) — fixed in 7f956d6 — P2 — bugfix-parity

  • What WEB does: quotes the sanitized HTML body (with cid images re-attached inline) inside an editable quote island, localized "On … wrote:" header with Name <email> (components/email/email-composer.tsx:462-500, lib/quote-header.ts:54-91; changelog 1.7.1, 1.7.3, 1.8.1).
  • What RN does: buildInitialHtml supports htmlBody (src/lib/compose-html.ts:79-83) but the viewer only passes body: plainTextBody(email) (src/screens/EmailThreadScreen.tsx:377), and the header uses display name only (compose-html.ts:31-35) rather than WEB's Name <email> (#482).
  • Fix hint: pass htmlBody (sanitized via stripDangerousTags, cid refs rewritten to fetched data URIs or re-attached with the same cid) and switch senderName to the Name <email> form.

• Forward as attachment (.eml) missing — fixed in d2ed27f — P3 — missing

  • What WEB does: More menu "Forward as attachment" builds a message/rfc822 attachment referencing the original blobId with a {date}-{subject}.eml name (lib/forward-as-attachment.ts:38-58, components/mail/mail-app.tsx:2022-2060; changelog 1.8.1).
  • What RN does: none.
  • Fix hint: add a More-sheet entry that opens Compose with attachments: [{blobId: email.blobId, name, type: 'message/rfc822', size: email.size}] (depends on the forward-attachments fix).

• Reply identity selection: exact match only, no +tag or catch-all domain override (#246) — fixed in 5b72c4d — P3 — partial

  • What WEB does: resolveReplyFrom — exact, then +tag-stripped, then same-domain catch-all with a From override (lib/reply-identity.ts:197-256).
  • What RN does: identities.find(i => i.email === candidate.email) (src/screens/ComposeScreen.tsx:431-437).
  • Fix hint: port resolveReplyFrom; the override needs a From override in sendEmail.

• Quick reply box under the message — fixed in d2ed27f — P3 — missing

  • What WEB does: inline textarea with Send / "More options" (opens composer prefilled), Ctrl+Enter (components/email/email-viewer.tsx:5066-5154).
  • What RN does: none.
  • Fix hint: optional; a bottom input that calls sendEmail with buildReplyRecipients output and the plain-text quote.

• View source: no copy-to-clipboard; whole raw message loaded into a <Text> — fixed in d2ed27f — P3 — partial

  • What WEB does: synthetic source from the JMAP object with a Copy button (components/email/email-viewer.tsx:5159-5208, lib/email-source.ts). RN's raw RFC 822 view is actually more faithful.
  • What RN does: fetches the full blob as text and renders it in one selectable Text (src/screens/EmailSourceScreen.tsx:24-35, 68-70); a 30 MB message will stall the JS thread.
  • Fix hint: add Clipboard.setStringAsync; cap display at e.g. 1 MB with a "Share full source" fallback.

• Add sender to contacts / edit contact from the viewer — fixed in d2ed27f — P3 — missing

  • What WEB does: contact sidebar with "Add to contacts"/"Edit" (components/email/email-viewer.tsx:552-568, 5336-5368; changelog 1.7.4).
  • What RN does: none (see popover finding).
  • Fix hint: sheet entry navigating to ContactForm with prefilled name/email.

Trusted senders / settings

• "Trust sender" writes to the Trusted Senders address book even when the setting is off — fixed in 06742ef — P3 — rn-only-bug

  • What WEB does: writes to the book only when trustedSendersAddressBook is on, else to the local list (components/email/email-viewer.tsx:4646-4655, components/trusted-senders-modal.tsx:136-140).
  • What RN does: always does both (src/components/EmailBodyView.tsx:644-653), and addToTrustedSendersBook creates the book on first add (src/stores/contacts-store.ts:308-321), so a user who left the setting off (default false, src/stores/settings-store.ts:239) still gets a server-side "Trusted Senders" address book; the settings modal then lists only the local entries (src/components/settings/ContentSendersSettings.tsx:19-21, 123-144), so book-trusted senders are invisible/unremovable there.
  • Fix hint: gate the book write on the setting (or, matching WEB 1.9.0, default the setting to on for contacts-capable accounts) and show trustedSenderEmails in the settings modal with remove support.

• S/MIME settings screen is a dead stub — fixed in 3d0d440 — P3 — rn-only-bug

  • What WEB does: built-in S/MIME was removed from core in 1.7.6 and lives in a privileged plugin; the viewer has no S/MIME state (components/email/email-viewer.tsx:923-937).
  • What RN does: SmimeSettings renders empty mock arrays and buttons with no handlers (src/components/settings/SmimeSettings.tsx:32-33, 118-121, 163-166); there is no verification/decryption in the viewer.
  • Fix hint: hide the screen (or show a "not available in the mobile app" note) until a crypto path exists; treat viewer-side S/MIME as N/A.

Verified at parity (brief list, so the fixer knows what NOT to redo)

• Body isolation: sandboxed WebView with default-src 'none' CSP, originWhitelist about:blank, links opened externally, no cookies/storage/file access (src/components/EmailBodyView.tsx:675-724, src/lib/email-html.ts:236-256) — matches WEB's srcDoc iframe + CSP approach (1.6.7).
• hasMeaningfulHtmlBody text-alternative preference (src/lib/email-html.ts:353-362) — same regex as WEB lib/signature-utils.ts (only the same-partId guard is missing, see P1 finding).
• Dark mode: invert+hue-rotate with media re-invert, native-dark-mode detection, emoji re-invert pass, "Always view emails in light mode" setting (src/lib/email-html.ts:167-185, 197-199, src/components/EmailBodyView.tsx:64-157, 499-502) — only the CSS revision differs (see finding).
• Plain-text path: escaped + linkified, native dark colours without inversion (src/lib/email-html.ts:120-126, 263-311).
• External content policy ask/block/allow, per-message "Load external content", "Trust sender" persisting locally and to the address book, trusted list from the address book and contacts (src/components/EmailBodyView.tsx:480-535, 643-672).
• cid inline images fetched with auth and injected as data URIs, transparent placeholder otherwise (src/components/EmailBodyView.tsx:546-584, src/lib/email-html.ts:213-218).
• Shrink-to-fit of fixed-width emails + in-page pinch zoom/pan with pager/scroll locking (src/components/EmailBodyView.tsx:159-460) — RN-only, better than WEB's horizontal scroll (#409).
• Mark read on open with delay setting (apart from the -1 bug), optimistic star/unread/tag toggles, delete/archive/spam/not-spam/move scoped to the message's account, no trash folder alert (src/screens/EmailThreadScreen.tsx:221-364). The account scoping was wrong for messages opened from the Unified Inbox, a notification or a deep link until 5c7301b (audit B3); star, tag and unread are queued offline since ddff2f7.
• Prev/next navigation with prefetched neighbour panes and swipe (src/screens/EmailThreadScreen.tsx:122-181, 535-572) — RN-only pager.
• Skeleton while loading (src/screens/EmailThreadScreen.tsx:845-886).
• Attachments: chips with size, show-all toggle, hideInlineImageAttachments setting, attachmentPosition setting, mailAttachmentAction preview/download, templated filenames + transforms identical to WEB (src/lib/download-filename.ts diff vs lib/download-filename.ts is whitespace/quotes only, minus DEFAULT_BUNDLE_TEMPLATE/BUNDLE_TOKENS), Downloads settings screen with live preview (src/components/settings/DownloadsSettings.tsx).
• Attachment/blob/source/.eml fetches routed by owner account for shared/group messages (src/screens/EmailThreadScreen.tsx:87-96, 198-215, src/api/blob.ts:119-135, src/lib/email-export.ts) — #847/#867 parity except the calendar banner.
• Client-cert-aware downloads via secureFetch, streaming download via File.downloadFileAsync (src/lib/email-export.ts:85-113).
• View source (raw RFC 822, shareable) and Export .eml with the email filename template (src/screens/EmailSourceScreen.tsx, src/lib/email-export.ts:173-206).
• Calendar invitation: detection by MIME/extension, parse via CalendarEvent/parse, RSVP via import-then-rsvpEvent with replyTo/organizerCalendarAddress, cancelled notice, "no writable calendar" warning, calendarInvitationParsingEnabled setting (src/components/email/CalendarInvitationBanner.tsx, src/lib/calendar-invitation.ts).
• Tag sheet from the viewer with keyword definitions (src/screens/EmailThreadScreen.tsx:1033-1100).

N/A on mobile

• Print (WEB handlePrint, components/email/email-viewer.tsx:2621-2670) — could be done with expo-print later, but not a parity requirement.
• Copy permalink to a message (#733) — RN opens incoming message links since 5802cae (src/navigation/linking.ts) but has no "copy link" action.
• Fullscreen reading toggle, Pro split panes, toolbar overflow measurement, plugin slots/hooks (email-banner, email-detail-sidebar, onRenderEmailBody, onBeforeExternalLink, ui.rerenderEmail), keyboard shortcuts, drag attachments out to the file system (#267), drag emails out as .eml, import .eml from the viewer menu (RN imports from the list screen instead).
• Iframe-specific fixes: "Render the email body on DOM parse instead of iframe load" (#635), iframe flash/flicker fixes (1.5.4, 1.6.7), blob: in CSP object-src/frame-src for PDF previews (#253), pdf.js bytes vs blob: fetch (#871), RSC 307 loop (#919), iOS Safari viewport zoom on input focus (#838).
• Demo-mode welcome pane, tour, contact sidebar panel layout (desktop only; the actions themselves are listed above).
• S/MIME plugin UI (WEB core has none since 1.7.6); listed above only because RN ships a misleading stub.