diff --git a/components/email/__tests__/conversation-pane.test.tsx b/components/email/__tests__/conversation-pane.test.tsx
new file mode 100644
index 000000000..2383f9a0b
--- /dev/null
+++ b/components/email/__tests__/conversation-pane.test.tsx
@@ -0,0 +1,110 @@
+import { render, screen, fireEvent } from '@testing-library/react';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import type { Email, Mailbox } from '@/lib/jmap/types';
+import { useSettingsStore } from '@/stores/settings-store';
+
+// The default layout's reading pane shows the whole conversation, as Mountain
+// View does: the newest message open, the older ones folded to a line each
+// and unfolded in place. Without `conversationPane` it shows the message alone.
+
+vi.mock('@/hooks/use-media-query', () => ({
+  useDeviceDetection: () => ({ isMobile: false, isTablet: false, isDesktop: true }),
+  useMediaQuery: () => false,
+}));
+vi.mock('@/components/tour/tour-provider', () => ({
+  useTour: () => ({ activeTour: null, startTour: vi.fn(), endTour: vi.fn(), registerStep: vi.fn() }),
+}));
+vi.mock('@/components/plugins/plugin-slot', () => ({ PluginSlot: () => null }));
+vi.mock('@/hooks/use-plugin-slot-offers', () => ({ usePluginSlotOffers: () => [] }));
+vi.stubGlobal('ResizeObserver', class { observe() {} unobserve() {} disconnect() {} });
+
+const { EmailViewer } = await import('../email-viewer');
+
+const mailboxes = [
+  { id: 'inbox', name: 'Inbox', role: 'inbox', parentId: null, myRights: { mayAddItems: true } },
+] as unknown as Mailbox[];
+
+function mail(n: number, overrides: Partial<Email> = {}): Email {
+  return {
+    id: `m${n}`, blobId: `b${n}`, threadId: 't1', mailboxIds: { inbox: true }, keywords: { $seen: true },
+    from: [{ name: `Sender ${n}`, email: `s${n}@example.com` }], to: [{ name: 'Me', email: 'me@example.com' }],
+    subject: 'Offsite agenda', receivedAt: `2026-01-0${n}T10:00:00Z`, preview: `Preview ${n}`,
+    hasAttachment: false, size: 100, ...overrides,
+  } as unknown as Email;
+}
+function withBody(e: Email, text: string): Email {
+  return {
+    ...e, textBody: [{ partId: '1', type: 'text/plain' }], htmlBody: [], attachments: [],
+    bodyValues: { '1': { value: text, isTruncated: false } },
+  } as unknown as Email;
+}
+
+const foldedIds = (c: HTMLElement) =>
+  [...c.querySelectorAll('[data-mv-conversation-card]')].map((e) => e.getAttribute('data-email-id'));
+const expandedIds = (c: HTMLElement) =>
+  [...c.querySelectorAll('[data-mv-conversation-expanded]')].map((e) => e.getAttribute('data-email-id'));
+
+function renderViewer(conversation: Email[], open: Email, props: Partial<Parameters<typeof EmailViewer>[0]> = {}) {
+  return render(
+    <EmailViewer
+      email={open}
+      mailboxes={mailboxes}
+      selectedMailbox="inbox"
+      currentMailboxRole="inbox"
+      mvConversation={conversation}
+      {...props}
+    />,
+  );
+}
+
+describe('The conversation in the default layout\'s reading pane', () => {
+  beforeEach(() => {
+    useSettingsStore.setState({ interfaceLayout: 'default', markAsReadDelay: 0 });
+  });
+
+  it('shows the older messages folded above the open newest one', () => {
+    const open = withBody(mail(6), 'Newest body');
+    const conversation = [mail(1), mail(2), mail(3), mail(4), mail(5), open];
+    const { container } = renderViewer(conversation, open, { conversationPane: true });
+
+    // A long run keeps its first and last message around a count.
+    expect(foldedIds(container)).toEqual(['m1', 'm5']);
+    expect(container.querySelector('[data-mv-conversation-before]')).not.toBeNull();
+    expect(screen.getByText('Newest body')).toBeInTheDocument();
+
+    // The count names what it does, and shows the rest.
+    fireEvent.click(screen.getByRole('button', { name: 'show_older' }));
+    expect(foldedIds(container)).toEqual(['m1', 'm2', 'm3', 'm4', 'm5']);
+  });
+
+  it('unfolds an older message in place and loads its body', () => {
+    const open = withBody(mail(3), 'Newest body');
+    const onLoad = vi.fn();
+    const { container } = renderViewer([mail(1), mail(2), open], open, {
+      conversationPane: true,
+      onLoadConversationEmail: onLoad,
+    });
+    fireEvent.click(screen.getByText('Sender 1'));
+    expect(expandedIds(container)).toEqual(['m1']);
+    expect(onLoad).toHaveBeenCalledWith(expect.objectContaining({ id: 'm1' }));
+  });
+
+  it('opens unread older messages unfolded and marks them read', () => {
+    const open = withBody(mail(3), 'Newest body');
+    const onRead = vi.fn();
+    const { container } = renderViewer([mail(1), mail(2, { keywords: {} }), open], open, {
+      conversationPane: true,
+      onMarkConversationEmailRead: onRead,
+    });
+    expect(expandedIds(container)).toEqual(['m2']);
+    expect(onRead).toHaveBeenCalledWith(expect.objectContaining({ id: 'm2' }));
+  });
+
+  it('shows the message alone without it ("Show emails as individual messages")', () => {
+    const open = withBody(mail(3), 'Newest body');
+    const { container } = renderViewer([mail(1), mail(2), open], open);
+    expect(foldedIds(container)).toEqual([]);
+    expect(container.querySelector('[data-mv-conversation-before]')).toBeNull();
+    expect(screen.getByText('Newest body')).toBeInTheDocument();
+  });
+});
diff --git a/components/email/__tests__/thread-list-item-conversation-pane.test.tsx b/components/email/__tests__/thread-list-item-conversation-pane.test.tsx
new file mode 100644
index 000000000..711ae9d2a
--- /dev/null
+++ b/components/email/__tests__/thread-list-item-conversation-pane.test.tsx
@@ -0,0 +1,97 @@
+import { render, screen, fireEvent } from '@testing-library/react';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { ThreadListItem } from '../thread-list-item';
+import { useSettingsStore, DEFAULT_KEYWORDS } from '@/stores/settings-store';
+import { useEmailStore } from '@/stores/email-store';
+import { useUIStore } from '@/stores/ui-store';
+import { groupEmailsByThread } from '@/lib/thread-utils';
+import type { Email } from '@/lib/jmap/types';
+
+// With the conversation in the reading pane, the list shows one row per
+// conversation: a click opens its newest message there, and the row has no
+// chevron to unfold it in the list.
+
+vi.mock('@/hooks/use-email-drag', () => ({
+  useEmailDrag: () => ({ dragHandlers: {}, isDragging: false }),
+}));
+vi.mock('@/stores/auth-store', () => {
+  const state = { identities: [], username: null, client: null, activeAccountId: null, getClientForAccount: () => undefined };
+  const useAuthStore = Object.assign(
+    (selector?: (s: typeof state) => unknown) => (selector ? selector(state) : state),
+    { getState: () => state },
+  );
+  return { useAuthStore };
+});
+
+const makeEmail = (overrides: Partial<Email> = {}): Email => ({
+  id: 'email-1', threadId: 't', mailboxIds: { inbox: true }, keywords: { $seen: true }, size: 1000,
+  receivedAt: '2024-01-15T10:00:00Z', from: [{ name: 'Alice', email: 'alice@example.com' }],
+  subject: 'Offsite agenda', hasAttachment: false, ...overrides,
+});
+const conversation = () => groupEmailsByThread([
+  makeEmail({ id: 'a', receivedAt: '2024-01-15T09:00:00Z' }),
+  makeEmail({ id: 'b', receivedAt: '2024-01-15T10:00:00Z', from: [{ name: 'Bob', email: 'bob@example.com' }] }),
+])[0];
+
+function renderRow(conversationInReader: boolean) {
+  const onEmailSelect = vi.fn();
+  const onToggleExpand = vi.fn();
+  const onCollapseAllThreads = vi.fn();
+  const thread = conversation();
+  render(
+    <ThreadListItem
+      thread={thread}
+      isExpanded={false}
+      onToggleExpand={onToggleExpand}
+      onCollapseAllThreads={onCollapseAllThreads}
+      onEmailSelect={onEmailSelect}
+      conversationInReader={conversationInReader}
+    />,
+  );
+  return { onEmailSelect, onToggleExpand, onCollapseAllThreads, thread };
+}
+
+beforeEach(() => {
+  useUIStore.setState({ isMobile: false, isTablet: false, isDesktop: true });
+  useSettingsStore.setState({
+    emailKeywords: [...DEFAULT_KEYWORDS], showPreview: true, mailLayout: 'split',
+    interfaceLayout: 'default', listColumns: false,
+  });
+  useEmailStore.setState({ selectedEmailKeys: new Set<string>(), selectedMailbox: 'inbox', isUnifiedView: false });
+});
+
+describe('A conversation row with the conversation in the reading pane', () => {
+  it('opens the newest message without unfolding the conversation in the list', () => {
+    const { onEmailSelect, onToggleExpand, onCollapseAllThreads, thread } = renderRow(true);
+    fireEvent.click(screen.getByRole('row'));
+    expect(onEmailSelect).toHaveBeenCalledWith(thread.latestEmail);
+    expect(onToggleExpand).not.toHaveBeenCalled();
+    expect(onCollapseAllThreads).not.toHaveBeenCalled();
+  });
+
+  it('has no chevron and does not claim to unfold', () => {
+    renderRow(true);
+    expect(screen.queryByRole('button', { name: /expand_named/ })).toBeNull();
+    expect(screen.getByRole('row')).not.toHaveAttribute('aria-expanded');
+  });
+
+  it('has no chevron in the columns layout either', () => {
+    useSettingsStore.setState({ mailLayout: 'horizontal', listColumns: true });
+    renderRow(true);
+    expect(screen.queryByRole('button', { name: /expand_named/ })).toBeNull();
+  });
+
+  it('still ticks the whole conversation with Ctrl+click', () => {
+    const { onEmailSelect } = renderRow(true);
+    fireEvent.click(screen.getByRole('row'), { ctrlKey: true });
+    expect(useEmailStore.getState().selectedEmailKeys.size).toBe(2);
+    expect(onEmailSelect).not.toHaveBeenCalled();
+  });
+
+  it('unfolds in the list when the reading pane shows one message', () => {
+    const { onToggleExpand } = renderRow(false);
+    expect(screen.getByRole('button', { name: /expand_named/ })).toBeTruthy();
+    fireEvent.click(screen.getByRole('row'));
+    expect(onToggleExpand).toHaveBeenCalled();
+  });
+});
diff --git a/components/email/email-list.tsx b/components/email/email-list.tsx
index 05d7ba06c..aaeda774e 100644
--- a/components/email/email-list.tsx
+++ b/components/email/email-list.tsx
@@ -87,6 +87,11 @@ interface EmailListProps {
   hasMore?: boolean;
   isLoadingMoreItems?: boolean;
   onOpenConversation?: (thread: ThreadGroup) => void;
+  /**
+   * The reading pane shows the whole conversation: a row opens its newest
+   * message there instead of unfolding the thread in the list.
+   */
+  conversationInReader?: boolean;
   onReply?: (email: Email) => void;
   onReplyAll?: (email: Email) => void;
   onForward?: (email: Email) => void;
@@ -164,6 +169,7 @@ export function EmailList({
   hasMore,
   isLoadingMoreItems,
   onOpenConversation,
+  conversationInReader = false,
   onReply,
   onReplyAll,
   onForward,
@@ -456,14 +462,14 @@ export function EmailList({
     const rows: ListRow[] = [];
     for (const thread of threadGroups) {
       rows.push({ key: emailKeyFor(thread.latestEmail), members: thread.emails.map(emailKeyFor) });
-      if (thread.emails.length > 1 && expandedThreadIds.has(thread.threadKey) && !isMobile) {
+      if (thread.emails.length > 1 && expandedThreadIds.has(thread.threadKey) && !isMobile && !conversationInReader) {
         for (const email of threadEmailsCache.get(thread.threadKey) ?? thread.emails) {
           rows.push({ key: emailKeyFor(email), members: [emailKeyFor(email)] });
         }
       }
     }
     setListRows(rows);
-  }, [threadGroups, expandedThreadIds, threadEmailsCache, isMobile, setListRows]);
+  }, [threadGroups, expandedThreadIds, threadEmailsCache, isMobile, conversationInReader, setListRows]);
   useEffect(() => () => setListRows(null), [setListRows]);
 
   // The virtualizer's guesses follow the rows' shape (see useListRowShape).
@@ -1013,7 +1019,8 @@ export function EmailList({
         )}
         {thread && <MemoizedThreadListItem
           thread={thread}
-          isExpanded={expandedThreadIds.has(thread.threadKey)}
+          isExpanded={!conversationInReader && expandedThreadIds.has(thread.threadKey)}
+          conversationInReader={conversationInReader}
           selectedEmailKey={selectedEmailKey}
           isLoading={isLoadingThread === thread.threadKey}
           expandedEmails={threadEmailsCache.get(thread.threadKey)}
diff --git a/components/email/email-viewer.tsx b/components/email/email-viewer.tsx
index e426a956d..db32890d1 100644
--- a/components/email/email-viewer.tsx
+++ b/components/email/email-viewer.tsx
@@ -281,6 +281,11 @@ interface EmailViewerProps {
    * fold and unfold in place, as Gmail does; unread ones start unfolded.
    */
   mvConversation?: Email[];
+  /**
+   * The default layout's reading pane shows `mvConversation` around the open
+   * message too, in its own look (not on phones, which have their own view).
+   */
+  conversationPane?: boolean;
   /**
    * Mountain View: the open message's conversation is still on its way. The
    * viewer waits for it rather than showing the message alone first. (#1223)
@@ -1024,6 +1029,7 @@ export function MvConversationRun({ emails, onOpen, timeFormat, collapseLongRun,
   expandedIds?: ReadonlySet<string>;
   renderExpanded?: (email: Email) => React.ReactNode;
 }) {
+  const tPane = useTranslations('conversation_pane');
   const [showAll, setShowAll] = useState(false);
   if (emails.length === 0) return null;
   const isExpanded = (e: Email) => !!renderExpanded && !!expandedIds?.has(e.id);
@@ -1041,6 +1047,8 @@ export function MvConversationRun({ emails, onOpen, timeFormat, collapseLongRun,
         <button
           type="button"
           onClick={() => setShowAll(true)}
+          aria-label={tPane('show_older', { count: middle.length })}
+          title={tPane('show_older', { count: middle.length })}
           data-mv-conversation-more=""
           className="absolute start-6 top-1/2 -translate-y-1/2 grid place-items-center w-10 h-10 rounded-full border border-border bg-background text-sm text-muted-foreground hover:bg-muted transition-colors"
         >
@@ -1357,6 +1365,7 @@ export function EmailViewer({
   mvPosition,
   mvFolderName,
   mvConversation,
+  conversationPane,
   mvConversationPending,
   onLoadConversationEmail,
   onMarkConversationEmailRead,
@@ -1506,10 +1515,12 @@ export function EmailViewer({
   // and has no bar fixed at the bottom; previous / next move to the top bar.
   const mvMobileViewer = interfaceLayout === 'mountain-view' && isMobile;
   const mvReplyRow = mvViewer || mvMobileViewer;
+  // Where the open message is read inside its conversation.
+  const conversationViewer = mvViewer || mvMobileViewer || (!!conversationPane && !isMobile);
   // The phone's bottom action bar: toasts sit above it.
   const bottomBarRef = useBottomControls(isMobile && !mvMobileViewer);
   // The open conversation around the open message, split at it.
-  const mvOpenIndex = (mvViewer || mvMobileViewer) && mvConversation && email ? mvConversation.findIndex((e) => e.id === email.id) : -1;
+  const mvOpenIndex = conversationViewer && mvConversation && email ? mvConversation.findIndex((e) => e.id === email.id) : -1;
   const mvBefore = mvOpenIndex > 0 ? mvConversation!.slice(0, mvOpenIndex) : [];
   const mvAfter = mvOpenIndex >= 0 ? mvConversation!.slice(mvOpenIndex + 1) : [];
   const mvConversationIds = mvOpenIndex >= 0 ? mvConversation!.map((e) => e.id).join(',') : '';
@@ -1556,7 +1567,7 @@ export function EmailViewer({
   // The conversation is not here yet (the one on hand is another thread's, or
   // none). Hold the message back instead of drawing it alone and then pushing
   // it down under the earlier messages.
-  const mvAwaitingConversation = !!mvConversationPending && (mvViewer || mvMobileViewer) && mvOpenIndex < 0;
+  const mvAwaitingConversation = !!mvConversationPending && conversationViewer && mvOpenIndex < 0;
   const renderMvExpanded = (target: Email) => (
     <MvExpandedConversationCard
       email={target}
@@ -5104,14 +5115,14 @@ ${printWatermark ? printWatermark.html : ''}
 
       {/* Mountain View: the conversation's earlier messages, folded. */}
       {mvBefore.length > 0 && (
-        <div data-mv-conversation-before="">
+        <div className="bg-background" data-mv-conversation-before="">
           <MvConversationRun emails={mvBefore} onOpen={toggleMvExpanded} expandedIds={mvExpandedIds} renderExpanded={renderMvExpanded} timeFormat={timeFormat} compact={mvMobileViewer} collapseLongRun />
         </div>
       )}
 
       {/* Mountain View: the open message folded like the rest of the conversation. */}
       {mvOpenFolded && email ? (
-        <div data-mv-open-folded="">
+        <div className="bg-background" data-mv-open-folded="">
           <MvConversationCard email={email} onOpen={() => setMvOpenFolded(false)} timeFormat={timeFormat} compact={mvMobileViewer} />
         </div>
       ) : mvAwaitingConversation ? (
@@ -5126,7 +5137,7 @@ ${printWatermark ? printWatermark.html : ''}
       ) : (<>
       {/* === SENDER INFO (Desktop) === */}
       <div
-        className={cn("hidden lg:block bg-background px-6", !mvViewer && "border-b border-border", mvViewer && mvBefore.length > 0 && "border-t border-border", mvOpenIndex >= 0 && "cursor-pointer")}
+        className={cn("hidden lg:block bg-background px-6", !mvViewer && "border-b border-border", (mvViewer || conversationPane) && mvBefore.length > 0 && "border-t border-border", mvOpenIndex >= 0 && "cursor-pointer")}
         style={mvViewer ? { paddingBlock: '0.75rem 0.5rem' } : { paddingBlock: 'var(--density-header-py)' }}
         data-mv-open-header={mvOpenIndex >= 0 ? "" : undefined}
         onClick={mvOpenIndex >= 0 ? (e) => {
@@ -6124,7 +6135,7 @@ ${printWatermark ? printWatermark.html : ''}
 
           {/* Mountain View: the conversation's later messages, folded. */}
           {mvAfter.length > 0 && (
-            <div className="mt-4 border-b border-border" data-mv-conversation-after="">
+            <div className="mt-4 border-b border-border bg-background" data-mv-conversation-after="">
               <MvConversationRun emails={mvAfter} onOpen={toggleMvExpanded} expandedIds={mvExpandedIds} renderExpanded={renderMvExpanded} timeFormat={timeFormat} compact={mvMobileViewer} />
             </div>
           )}
diff --git a/components/email/thread-list-item.tsx b/components/email/thread-list-item.tsx
index 6da3a94f8..42b420155 100644
--- a/components/email/thread-list-item.tsx
+++ b/components/email/thread-list-item.tsx
@@ -377,6 +377,8 @@ interface ThreadListItemProps {
   onPrefetch?: (email: Email) => void;
   onContextMenu?: (e: React.MouseEvent, email: Email) => void;
   onOpenConversation?: (thread: ThreadGroup) => void;
+  /** The reading pane shows the conversation: the row opens it there and never unfolds. */
+  conversationInReader?: boolean;
   onToggleStar?: (email: Email) => void;
   onMarkAsRead?: (email: Email, read: boolean) => void;
   onDelete?: (email: Email) => void;
@@ -1043,6 +1045,7 @@ export const ThreadListItem = React.forwardRef<HTMLDivElement, ThreadListItemPro
     onPrefetch,
     onContextMenu,
     onOpenConversation,
+    conversationInReader = false,
     onToggleStar,
     onMarkAsRead,
     onDelete,
@@ -1291,7 +1294,8 @@ export const ThreadListItem = React.forwardRef<HTMLDivElement, ThreadListItemPro
         return;
       }
 
-      if (mvRow || mvMobileRow) {
+      // So does the default layout, whose reading pane shows the conversation.
+      if (mvRow || mvMobileRow || conversationInReader) {
         // Desktop keeps the ticked rows while the conversation is read (#1231).
         onEmailSelect(latestEmail);
         return;
@@ -1345,7 +1349,7 @@ export const ThreadListItem = React.forwardRef<HTMLDivElement, ThreadListItemPro
             rowKey: emailKeyFor(latestEmail),
             label: a11yLabel,
             selected: isSelected && !isExpanded,
-            expanded: isExpanded,
+            expanded: conversationInReader ? undefined : isExpanded,
             checked: isChecked,
             selectionMode: selectedEmailKeys.size > 0,
             onToggleCheck: toggleThreadSelection,
@@ -1469,7 +1473,7 @@ export const ThreadListItem = React.forwardRef<HTMLDivElement, ThreadListItemPro
                     selectLabel={selectRowLabel}
                   />
                   {hasUnread && <UnreadDot besideAvatar />}
-                  {!isMobile && !columns && (
+                  {!isMobile && !columns && !conversationInReader && (
                     <button
                       data-expand-toggle
                       onClick={(e) => {
@@ -1523,6 +1527,10 @@ export const ThreadListItem = React.forwardRef<HTMLDivElement, ThreadListItemPro
                       // count follows the names, so a folded conversation is
                       // one line like any message. (#262)
                       <span data-list-from="" className={cn(LIST_COLUMN_CLASS.from, 'flex items-center gap-2 text-sm')}>
+                        {conversationInReader ? (
+                          // The reading pane shows the conversation: the chevron's room, as on a single message's row.
+                          <span aria-hidden="true" className="w-3.5 shrink-0" />
+                        ) : (
                         <button
                           data-expand-toggle
                           onClick={(e) => {
@@ -1541,6 +1549,7 @@ export const ThreadListItem = React.forwardRef<HTMLDivElement, ThreadListItemPro
                             <ChevronRight className="w-3.5 h-3.5" />
                           )}
                         </button>
+                        )}
                         {isUnifiedView && latestEmail.accountId && threadAccountColor && showAccountDot && (
                           <span
                             className="w-2 h-2 rounded-full flex-shrink-0"
diff --git a/components/mail/__tests__/blob-routing.test.tsx b/components/mail/__tests__/blob-routing.test.tsx
index 29c180bbb..4dd76465d 100644
--- a/components/mail/__tests__/blob-routing.test.tsx
+++ b/components/mail/__tests__/blob-routing.test.tsx
@@ -135,7 +135,9 @@ beforeEach(() => {
     getClientForAccount: (id) => (id === 'login-primary' ? asClient(primary) : id === 'login-other' ? asClient(other) : undefined) as never,
     getAllConnectedClients: () => new Map([['login-primary', asClient(primary)], ['login-other', asClient(other)]]) as never,
   });
-  useSettingsStore.setState({ interfaceLayout: 'default', markAsReadDelay: -1, enableUnifiedMailbox: false, mailAttachmentAction: 'download', mailLayout: 'split', attachmentImagePreviewsEnabled: false, postExportAction: 'none', attachmentDownloadTemplate: '{filename}', filenameLowercase: false } as never);
+  // One message in the reader: fetching its conversation would take the
+  // requests these tests count.
+  useSettingsStore.setState({ interfaceLayout: 'default', markAsReadDelay: -1, enableUnifiedMailbox: false, mailAttachmentAction: 'download', mailLayout: 'split', attachmentImagePreviewsEnabled: false, postExportAction: 'none', attachmentDownloadTemplate: '{filename}', filenameLowercase: false, disableThreading: true } as never);
   useEmailStore.setState({
     emails: [message()], selectedEmail: message(), selectedMailbox: sharedMailbox.id,
     mailboxes: [primaryMailbox, sharedMailbox], viewingAccountId: null, accountMailboxes: {},
diff --git a/components/mail/__tests__/mail-app-conversation-pane.test.tsx b/components/mail/__tests__/mail-app-conversation-pane.test.tsx
new file mode 100644
index 000000000..e26eeca3e
--- /dev/null
+++ b/components/mail/__tests__/mail-app-conversation-pane.test.tsx
@@ -0,0 +1,218 @@
+import React, { Suspense, lazy } from 'react';
+import { act, fireEvent, render, screen, waitFor } from '@testing-library/react';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import type { Email, Mailbox } from '@/lib/jmap/types';
+import { useAuthStore } from '@/stores/auth-store';
+import { useEmailStore } from '@/stores/email-store';
+import { useSettingsStore } from '@/stores/settings-store';
+import { usePluginStore } from '@/stores/plugin-store';
+import { useThemeStore } from '@/stores/theme-store';
+import { useToastStore } from '@/stores/toast-store';
+import { DEFAULT_SEARCH_FILTERS } from '@/lib/jmap/search-utils';
+import { clearAllHooks } from '@/lib/plugin-hooks';
+import { forgetEmailPrefetches } from '@/lib/email-prefetch';
+
+// The default layout's reading pane shows the open message's conversation, on
+// every layout but a phone's, and j / k go on from the last message opened.
+
+vi.mock('next/dynamic', () => ({ default: (load: () => Promise<React.ComponentType<Record<string, unknown>>>) => {
+  const Component = lazy(async () => ({ default: await load() }));
+  return function Dynamic(props: Record<string, unknown>) {
+    return <Suspense fallback={null}><Component {...props} /></Suspense>;
+  };
+} }));
+type ViewerProps = { mvConversation?: { id: string }[]; conversationPane?: boolean };
+vi.mock('@/components/email/email-viewer', () => ({
+  EmailViewer: ({ mvConversation, conversationPane }: ViewerProps) => (
+    <div data-testid="reader" data-pane={conversationPane ? 'conversation' : 'message'}>
+      {mvConversation ? mvConversation.map((e) => e.id).join(',') : 'no conversation'}
+    </div>
+  ),
+}));
+vi.mock('@/components/email/email-composer', () => ({ EmailComposer: () => null }));
+vi.mock('@/components/layout/sidebar', () => ({ Sidebar: () => null }));
+vi.mock('@/components/layout/navigation-rail', () => ({ NavigationRail: () => null }));
+vi.mock('@/components/layout/calendar-event-notification-toaster', () => ({ CalendarEventNotificationToaster: () => null }));
+vi.mock('@/components/layout/share-notification-toaster', () => ({ ShareNotificationToaster: () => null }));
+vi.mock('@/components/layout/mobile-header', () => ({ MobileHeader: () => null }));
+vi.mock('@/components/layout/mv-top-bar', () => ({ MvTopBar: () => null }));
+vi.mock('@/components/layout/mv-side-panel', () => ({ MvSidePanel: () => null }));
+vi.mock('@/components/email/message-list-tabs', () => ({ useMessageListPanelProps: (id: string) => ({ id }), MessageListTabs: () => null }));
+vi.mock('@/components/search/search-box', () => ({ SearchBox: () => <input aria-label="stub search field" data-search-input /> }));
+vi.mock('@/components/tour/tour-provider', () => ({ useTour: () => ({ activeTour: null, registerStep: vi.fn() }) }));
+vi.mock('@/components/plugins/plugin-slot', () => ({ PluginSlot: () => null }));
+vi.mock('@/hooks/use-plugin-slot-offers', () => ({ usePluginSlotOffers: () => [] }));
+vi.mock('@/hooks/use-config', () => ({ useConfig: () => ({ appName: 'Mail' }) }));
+vi.mock('@/hooks/use-identity-sync', () => ({ useIdentitySync: () => {} }));
+vi.mock('@/hooks/use-pro-multi-account-identities', () => ({ useProMultiAccountIdentities: () => [] }));
+vi.mock('@/hooks/use-pro-multi-account-mailboxes', () => ({ useProMultiAccountMailboxes: () => {} }));
+vi.mock('@/hooks/use-wopi-status', () => ({ useWopiStatus: () => null, canWopiOpen: () => false }));
+vi.mock('@/hooks/use-browser-navigation', () => ({ useBrowserNavigation: () => {} }));
+vi.mock('@/hooks/use-media-query', () => ({
+  useDeviceDetection: () => ({ isMobile: false, isTablet: false, isDesktop: true }),
+  useMediaQuery: () => false,
+  useIsDesktop: () => true,
+}));
+vi.mock('@/lib/push-bindings', () => ({ reconcilePushBindings: () => {}, releasePushBindings: () => {} }));
+vi.mock('@/components/email/email-list', () => ({ EmailList: () => <div>message list</div> }));
+
+const { MailApp } = await import('../mail-app');
+
+function mailbox(id: string, role: string): Mailbox {
+  return {
+    id, name: role, role, sortOrder: 0, totalEmails: 3, unreadEmails: 0, totalThreads: 3, unreadThreads: 0, isSubscribed: true,
+  } as Mailbox;
+}
+const folders = [
+  mailbox('inbox', 'inbox'), mailbox('archive', 'archive'), mailbox('trash', 'trash'),
+  mailbox('junk', 'junk'), mailbox('work', ''),
+];
+const row = (id: string, minute: number, mailboxIds: Record<string, boolean> = { inbox: true }) => ({
+  id, threadId: `t-${id}`, subject: id, receivedAt: new Date(Date.UTC(2026, 9, 31, 10, minute)).toISOString(),
+  keywords: { $seen: true }, mailboxIds,
+}) as unknown as Email;
+const inbox = () => [row('m1', 30), row('m2', 20), row('m3', 10)];
+
+let client: Record<string, ReturnType<typeof vi.fn> | (() => unknown)>;
+let fetchEmailContent: ReturnType<typeof vi.fn>;
+// Every message the store had open, in order.
+let opened: (string | null)[];
+let unsubscribe: () => void;
+
+beforeEach(() => {
+  vi.stubGlobal('fetch', vi.fn().mockRejectedValue(new Error('Unexpected network request')));
+  vi.stubGlobal('ResizeObserver', class { observe() {} unobserve() {} disconnect() {} });
+  usePluginStore.setState({ initializePlugins: vi.fn().mockResolvedValue(undefined) });
+  useThemeStore.setState({ syncServerThemes: vi.fn().mockResolvedValue(undefined) });
+  useToastStore.setState({ toasts: [] });
+  clearAllHooks();
+  forgetEmailPrefetches();
+  client = {
+    getAccountId: () => 'acc', getUsername: () => 'a@example.org',
+    getSieveAccountId: () => null, hasDelayedSend: () => false, getSession: () => null,
+    getMailboxes: vi.fn().mockResolvedValue(folders),
+    getThread: vi.fn(async (threadId: string) => ({ id: threadId, emailIds: [threadId.slice(2)] })),
+    getEmail: vi.fn(async (id: string) => ({ ...inbox().find((e) => e.id === id)!, bodyValues: {} })),
+    moveEmail: vi.fn().mockResolvedValue(undefined),
+    moveToTrash: vi.fn().mockResolvedValue(undefined),
+    markAsRead: vi.fn().mockResolvedValue(undefined),
+    markAsSpam: vi.fn().mockResolvedValue(undefined),
+    undoSpam: vi.fn().mockResolvedValue(undefined),
+    removeEmailsFromMailbox: vi.fn().mockResolvedValue(undefined),
+  };
+  useAuthStore.setState({
+    isAuthenticated: true, isLoading: false, client: client as never, activeAccountId: 'login-a', identities: [],
+    getClientForAccount: (id: string) => (id === 'login-a' ? client : undefined) as never,
+    getAllConnectedClients: () => new Map([['login-a', client]]) as never,
+  });
+  useSettingsStore.setState({
+    enableUnifiedMailbox: false, interfaceLayout: 'default', mailLayout: 'focus', archiveMode: 'single',
+    deleteAction: 'trash', returnToListAfterAction: true, confirmArchive: false, confirmDelete: false,
+    singleKeyShortcuts: true,
+  } as never);
+  fetchEmailContent = vi.fn().mockResolvedValue(undefined);
+  const emails = inbox();
+  useEmailStore.setState({
+    emails, selectedEmail: emails[0], selectedMailbox: 'inbox', selectedKeyword: null, mailboxes: folders,
+    viewingAccountId: null, accountMailboxes: {}, isUnifiedView: false, unifiedRole: null,
+    isScheduledView: false, isLoadingEmail: false, isLoading: false, searchQuery: '',
+    searchFilters: { ...DEFAULT_SEARCH_FILTERS }, searchMailboxId: '',
+    selectedEmailKeys: new Set(), unreadSection: null,
+    fetchMailboxes: vi.fn().mockResolvedValue(undefined), fetchEmails: vi.fn().mockResolvedValue(undefined),
+    fetchQuota: vi.fn().mockResolvedValue(undefined), fetchTagCounts: vi.fn().mockResolvedValue(undefined),
+    refreshScheduledMetadata: vi.fn().mockResolvedValue(undefined),
+    fetchEmailContent,
+  } as never);
+  opened = [];
+  unsubscribe = useEmailStore.subscribe((state, prev) => {
+    if (state.selectedEmail !== prev.selectedEmail) opened.push(state.selectedEmail?.id ?? null);
+  });
+});
+afterEach(() => {
+  unsubscribe();
+  vi.restoreAllMocks();
+  vi.unstubAllGlobals();
+});
+
+const selectedId = () => useEmailStore.getState().selectedEmail?.id ?? null;
+const press = (key: string) => act(() => { fireEvent.keyDown(window, { key }); });
+
+describe('The reading pane in the default layout', () => {
+  beforeEach(() => {
+    useSettingsStore.setState({ interfaceLayout: 'default', mailLayout: 'split', disableThreading: false } as never);
+    client.getThread = vi.fn(async (threadId: string) => ({
+      id: threadId, emailIds: threadId === 't-m1' ? ['m0', 'm1'] : [threadId.slice(2)],
+    }));
+    client.getSomeEmails = vi.fn(async (ids: string[]) => ids.map((id) => (id === 'm0'
+      ? { ...row('m0', 0), threadId: 't-m1', mailboxIds: { sent: true } }
+      : { ...inbox().find((e) => e.id === id)!, threadId: 't-m1' })));
+  });
+
+  it('shows the whole conversation of the open message', async () => {
+    render(<MailApp />);
+    const reader = await screen.findByTestId('reader', {}, { timeout: 5000 });
+    expect(reader).toHaveAttribute('data-pane', 'conversation');
+    await waitFor(() => expect(reader).toHaveTextContent('m0,m1'));
+  });
+
+  it('shows the message alone with "Show emails as individual messages"', async () => {
+    useSettingsStore.setState({ disableThreading: true } as never);
+    render(<MailApp />);
+    const reader = await screen.findByTestId('reader', {}, { timeout: 5000 });
+    expect(reader).toHaveAttribute('data-pane', 'message');
+    await act(async () => { await new Promise((resolve) => setTimeout(resolve, 50)); });
+    expect(reader).toHaveTextContent('no conversation');
+    expect(client.getThread).not.toHaveBeenCalled();
+  });
+
+  it('does not unfold the conversation in the list with x', async () => {
+    useEmailStore.setState({ expandedThreadIds: new Set(), fetchThreadEmails: vi.fn().mockResolvedValue(undefined) } as never);
+    render(<MailApp />);
+    await screen.findByTestId('reader', {}, { timeout: 5000 });
+    await press('x');
+    expect(useEmailStore.getState().expandedThreadIds.size).toBe(0);
+  });
+});
+
+describe('j and k after Escape', () => {
+  beforeEach(() => {
+    useSettingsStore.setState({ interfaceLayout: 'default', mailLayout: 'split' } as never);
+    useEmailStore.setState({ listRows: null } as never);
+  });
+
+  it('j opens the message after the one that was open, not the first', async () => {
+    render(<MailApp />);
+    await screen.findByTestId('reader', {}, { timeout: 5000 });
+    await press('j');
+    await waitFor(() => expect(selectedId()).toBe('m2'));
+    await press('Escape');
+    await waitFor(() => expect(selectedId()).toBeNull());
+    await press('j');
+    await waitFor(() => expect(selectedId()).toBe('m3'));
+  });
+
+  it('k opens the message before it', async () => {
+    useEmailStore.setState({ selectedEmail: inbox()[2] } as never);
+    render(<MailApp />);
+    await screen.findByTestId('reader', {}, { timeout: 5000 });
+    await press('Escape');
+    await waitFor(() => expect(selectedId()).toBeNull());
+    await press('k');
+    await waitFor(() => expect(selectedId()).toBe('m2'));
+  });
+
+  it('steps by conversation, in the order of the list', async () => {
+    useEmailStore.setState({
+      listRows: [{ key: 'm1', members: ['m1', 'm3'] }, { key: 'm2', members: ['m2'] }],
+    } as never);
+    render(<MailApp />);
+    await screen.findByTestId('reader', {}, { timeout: 5000 });
+    await press('j');
+    await waitFor(() => expect(selectedId()).toBe('m2'));
+    await press('j');
+    await act(async () => { await new Promise((resolve) => setTimeout(resolve, 50)); });
+    expect(selectedId()).toBe('m2');
+    await press('k');
+    await waitFor(() => expect(selectedId()).toBe('m1'));
+  });
+});
diff --git a/components/mail/__tests__/mail-app-return-to-list.test.tsx b/components/mail/__tests__/mail-app-return-to-list.test.tsx
index 6f64a44b3..84b280902 100644
--- a/components/mail/__tests__/mail-app-return-to-list.test.tsx
+++ b/components/mail/__tests__/mail-app-return-to-list.test.tsx
@@ -273,6 +273,75 @@ describe.each([
   });
 });
 
+// With the list beside the reading pane (split, horizontal) the setting,
+// while nobody has changed it, opens the next message instead, as Outlook
+// does. A choice the user made wins, on every layout and device.
+describe('Archive with the list beside the reading pane', () => {
+  beforeEach(() => {
+    useSettingsStore.setState({ interfaceLayout: 'default', mailLayout: 'split', explicitSettings: [] } as never);
+    useEmailStore.setState({ listRows: null } as never);
+  });
+
+  it('opens the next message while the setting is untouched', async () => {
+    render(<MailApp />);
+    fireEvent.click(await screen.findByText('stub archive', {}, { timeout: 5000 }));
+    await waitFor(() => expect(client.moveEmail).toHaveBeenCalledWith('m1', 'archive', undefined));
+    await waitFor(() => expect(selectedId()).toBe('m2'));
+  });
+
+  it('opens the next row in the order the list shows', async () => {
+    useEmailStore.setState({
+      listRows: [{ key: 'm1', members: ['m1'] }, { key: 'm3', members: ['m3'] }, { key: 'm2', members: ['m2'] }],
+    } as never);
+    render(<MailApp />);
+    fireEvent.click(await screen.findByText('stub archive', {}, { timeout: 5000 }));
+    await waitFor(() => expect(client.moveEmail).toHaveBeenCalledWith('m1', 'archive', undefined));
+    await waitFor(() => expect(selectedId()).toBe('m3'));
+    expect(opened).not.toContain('m2');
+  });
+
+  it('goes back to the list when the user switched the setting on', async () => {
+    useSettingsStore.setState({ returnToListAfterAction: true, explicitSettings: ['returnToListAfterAction'] } as never);
+    render(<MailApp />);
+    fireEvent.click(await screen.findByText('stub archive', {}, { timeout: 5000 }));
+    await waitFor(() => expect(useEmailStore.getState().emails.map((e) => e.id)).toEqual(['m2', 'm3']));
+    expect(selectedId()).toBeNull();
+    expect(opened).not.toContain('m2');
+  });
+
+  it('opens the archived message again on Undo', async () => {
+    client.restoreEmails = vi.fn().mockResolvedValue(undefined);
+    useEmailStore.setState({
+      refreshCurrentMailbox: vi.fn(async () => { useEmailStore.setState({ emails: inbox() } as never); }),
+    } as never);
+    render(<MailApp />);
+    fireEvent.click(await screen.findByText('stub archive', {}, { timeout: 5000 }));
+    await waitFor(() => expect(selectedId()).toBe('m2'));
+    const archived = await waitFor(() => {
+      const found = useToastStore.getState().toasts.find((toast) => toast.title === 'notifications.email_archived');
+      expect(found?.action).toBeTruthy();
+      return found!;
+    });
+    act(() => { archived.action!.onClick(); });
+    await waitFor(() => expect(client.restoreEmails).toHaveBeenCalled());
+    await waitFor(() => expect(selectedId()).toBe('m1'));
+  });
+});
+
+describe('Delete with the list beside the reading pane', () => {
+  beforeEach(() => {
+    useSettingsStore.setState({ interfaceLayout: 'default', mailLayout: 'horizontal', explicitSettings: [] } as never);
+    useEmailStore.setState({ listRows: null } as never);
+  });
+
+  it('opens the next message while the setting is untouched', async () => {
+    render(<MailApp />);
+    fireEvent.click(await screen.findByText('stub delete', {}, { timeout: 5000 }));
+    await waitFor(() => expect(client.moveToTrash).toHaveBeenCalled());
+    await waitFor(() => expect(selectedId()).toBe('m2'));
+  });
+});
+
 describe('A list collapsed under an open message (focused layout)', () => {
   const list = () => screen.getByText('message list').closest('section')!;
 
diff --git a/components/mail/__tests__/mail-app-thread-expand-mark-read.test.tsx b/components/mail/__tests__/mail-app-thread-expand-mark-read.test.tsx
index eb1b03844..f8162531e 100644
--- a/components/mail/__tests__/mail-app-thread-expand-mark-read.test.tsx
+++ b/components/mail/__tests__/mail-app-thread-expand-mark-read.test.tsx
@@ -11,7 +11,9 @@ import { DEFAULT_SEARCH_FILTERS } from '@/lib/jmap/search-utils';
 
 // The `x` shortcut expands the selected conversation and marks it read. It has
 // to follow markAsReadDelay like the reading pane, and a delayed mark must not
-// land once the user has moved on (`j`/`k`) to a message outside it.
+// land once the user has moved on (`j`/`k`) to a message outside it. The
+// default layout shows the conversation in the reading pane instead, so this
+// runs where the list still unfolds it: Mountain View on a tablet.
 
 vi.mock('@/components/email/email-composer', () => ({ EmailComposer: () => null }));
 vi.mock('@/components/email/email-viewer', () => ({ EmailViewer: () => null }));
@@ -32,7 +34,7 @@ vi.mock('@/hooks/use-pro-multi-account-mailboxes', () => ({ useProMultiAccountMa
 vi.mock('@/hooks/use-wopi-status', () => ({ useWopiStatus: () => null, canWopiOpen: () => false }));
 vi.mock('@/hooks/use-browser-navigation', () => ({ useBrowserNavigation: () => {} }));
 vi.mock('@/hooks/use-media-query', () => ({
-  useDeviceDetection: () => ({ isMobile: false, isTablet: false, isDesktop: true }),
+  useDeviceDetection: () => ({ isMobile: false, isTablet: true, isDesktop: false }),
   useMediaQuery: () => false,
   useIsDesktop: () => true,
   useIsMobile: () => false,
@@ -78,7 +80,7 @@ beforeEach(() => {
     getClientForAccount: () => client as never,
     getAllConnectedClients: () => new Map([['login', client]]) as never,
   });
-  useSettingsStore.setState({ enableUnifiedMailbox: false, mailLayout: 'split', interfaceLayout: 'default' } as never);
+  useSettingsStore.setState({ enableUnifiedMailbox: false, mailLayout: 'split', interfaceLayout: 'mountain-view' } as never);
   useEmailStore.setState({
     // The conversation's newest message is open (selected with `j`).
     emails: [...conversation, single], selectedEmail: conversation[0], selectedMailbox: inbox.id, mailboxes: [inbox],
diff --git a/components/mail/mail-app.tsx b/components/mail/mail-app.tsx
index 95a20cf08..f6a40413d 100644
--- a/components/mail/mail-app.tsx
+++ b/components/mail/mail-app.tsx
@@ -80,6 +80,8 @@ import { useMailStatusAnnouncements } from "@/hooks/use-mail-status-announcement
 import { cn, formatDateTime, getMailboxPath } from "@/lib/utils";
 import { localizeMailboxName } from "@/lib/mailbox-label";
 import { KEYWORD_PREFIX, KEYWORD_PREFIX_LEGACY, emailKeyFor, groupEmailsByThread, threadKeyFor } from "@/lib/thread-utils";
+import { stepListEmail } from "@/lib/list-step";
+import { listBesideReader, returnToListAfterAction } from "@/lib/return-to-list";
 import { resolveThreadRoute } from "@/lib/thread-routing";
 import {
   ErrorBoundary,
@@ -732,6 +734,13 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     [scheduledEmails, scheduledAccountScope],
   );
   const activeEmails = isScheduledView ? scopedScheduledEmails : emails;
+  // The default layout reads a thread as one conversation in the reading pane
+  // too, as Mountain View does, on every width but a phone's (those keep their
+  // own conversation view). The list then has one row per conversation.
+  // "Show emails as individual messages" keeps the single message.
+  const disableThreading = useSettingsStore((s) => s.disableThreading);
+  const paneConversationView = interfaceLayout !== 'mountain-view' && !isMobile && !disableThreading && !isScheduledView;
+  const readerConversationView = mvConversationView || paneConversationView;
   // In an account-scoped scheduled view the visible rows are a filtered subset
   // of the loaded page, so "has more" must reflect that account's own total
   // rather than the combined one — otherwise the list looks complete while
@@ -973,23 +982,33 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     );
   };
 
+  // The open message's list key, kept after the reader closes.
+  const lastOpenedKeyRef = useRef<string | null>(null);
+  useEffect(() => {
+    if (selectedEmail) lastOpenedKeyRef.current = emailKeyFor(selectedEmail);
+  }, [selectedEmail]);
   // Keyboard shortcuts handlers
+  // j / k go on from the open message, or from the last one opened once the
+  // reader is closed (Escape), not from the top. With the conversation in the
+  // reading pane they step by conversation, as the list's rows do.
+  const stepFrom = (direction: 1 | -1) => stepListEmail(
+    activeEmails,
+    selectedEmail ? emailKeyFor(selectedEmail) : lastOpenedKeyRef.current,
+    direction,
+    paneConversationView ? useEmailStore.getState().listRows : null,
+  );
   const keyboardHandlers = useMemo(() => ({
     onNextEmail: () => {
-      if (activeEmails.length === 0) return;
-      const currentIndex = selectedEmail ? activeEmails.findIndex(e => emailKeyFor(e) === emailKeyFor(selectedEmail)) : -1;
-      const nextIndex = currentIndex < activeEmails.length - 1 ? currentIndex + 1 : currentIndex;
-      if (nextIndex >= 0 && nextIndex < activeEmails.length) {
-        void handleEmailSelect(activeEmails[nextIndex]);
+      const next = stepFrom(1);
+      if (next) {
+        void handleEmailSelect(next);
         if (mvShell) setCursorOnly(true);
       }
     },
     onPreviousEmail: () => {
-      if (activeEmails.length === 0) return;
-      const currentIndex = selectedEmail ? activeEmails.findIndex(e => emailKeyFor(e) === emailKeyFor(selectedEmail)) : activeEmails.length;
-      const prevIndex = currentIndex > 0 ? currentIndex - 1 : 0;
-      if (prevIndex >= 0 && prevIndex < activeEmails.length) {
-        void handleEmailSelect(activeEmails[prevIndex]);
+      const previous = stepFrom(-1);
+      if (previous) {
+        void handleEmailSelect(previous);
         if (mvShell) setCursorOnly(true);
       }
     },
@@ -1242,7 +1261,8 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     // thread's messages and marks them read (following markAsReadDelay),
     // collapsing only toggles. (#683)
     onToggleThreadExpansion: () => {
-      if (isScheduledView || !client) return;
+      // The reading pane shows the conversation; the list never unfolds it.
+      if (isScheduledView || !client || paneConversationView) return;
       if (!selectedEmail?.threadId) return;
       const threadKey = threadKeyFor(selectedEmail);
       const store = useEmailStore.getState();
@@ -3330,12 +3350,41 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
   // holds (a quick filter dropped it) stays selected: the store finds it
   // through the selection (#695), and with no row to go on from it opens
   // nothing after it anyway. (#1458)
+  //
+  // Left alone, the setting follows the layout (lib/return-to-list): with the
+  // list beside the reading pane the next message opens instead, as in
+  // Outlook. With the conversation in the reading pane that is the next
+  // conversation down the list (the one above at the end), as its row opens it.
+  const returnsToList = () => returnToListAfterAction(
+    !fullscreenReading && listBesideReader({ mailLayout, interfaceLayout, isMobile, isTablet }),
+  );
   const leaveIfOpen = (email: Email) => {
-    const { selectedEmail: open, emails: rows } = useEmailStore.getState();
+    const { selectedEmail: open, emails: rows, listRows } = useEmailStore.getState();
     const key = emailKeyFor(email);
     if (!open || emailKeyFor(open) !== key || (mvShell && cursorOnly)) return;
     if (!rows.some((row) => emailKeyFor(row) === key)) return;
-    if (useSettingsStore.getState().returnToListAfterAction) handleMobileBack();
+    if (returnsToList()) {
+      handleMobileBack();
+      return;
+    }
+    if (!paneConversationView || !listRows) return;
+    const below = stepListEmail(rows, key, 1, listRows);
+    const next = below && emailKeyFor(below) !== key ? below : stepListEmail(rows, key, -1, listRows);
+    if (!next || emailKeyFor(next) === key || threadKeyFor(next) === threadKeyFor(email)) return;
+    handleMobileBack();
+    void handleEmailSelect(next);
+  };
+  // Undo puts back the message that was open, and opens it again, where it
+  // was open in the reading pane. Phones stay in the list.
+  const reopenEmailRef = useRef<((email: Email) => Promise<unknown>) | null>(null);
+  const reopenAfterUndo = (email: Email) => {
+    const { selectedEmail: open } = useEmailStore.getState();
+    if (isMobile || !open || emailKeyFor(open) !== emailKeyFor(email)) return undefined;
+    const key = emailKeyFor(email);
+    return () => {
+      const restored = useEmailStore.getState().emails.find((e) => emailKeyFor(e) === key);
+      if (restored) void reopenEmailRef.current?.(restored);
+    };
   };
 
   const handleDelete = async (emailToDelete: Email | null = selectedEmail) => {
@@ -3379,6 +3428,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
       return;
     }
 
+    const reopen = reopenAfterUndo(emailToDelete);
     leaveIfOpen(emailToDelete);
 
     // The store's delete reads the "Delete action" setting: move to the
@@ -3387,7 +3437,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     try {
       // false: a plugin stopped it and said why, so no "deleted" here.
       if (await deleteEmail(client, emailToDelete.id, isInTrash, emailKeyFor(emailToDelete))) {
-        toastWithUndo(permanent ? t('notifications.email_deleted') : t('mail_list_extra.moved_to_trash'), undoMoveAction(client, restore, undo));
+        toastWithUndo(permanent ? t('notifications.email_deleted') : t('mail_list_extra.moved_to_trash'), undoMoveAction(client, restore, undo, undefined, reopen));
       }
     } catch (error) {
       console.error("Failed to delete email:", error);
@@ -3487,6 +3537,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
       }
 
       let restore: EmailRestoreBatch[] | null = null;
+      const reopen = reopenAfterUndo(emailToArchive);
       leaveIfOpen(emailToArchive);
       const archived = await moveThreadToMailbox(client, emailToArchive.id, destination.id, emailKeyFor(emailToArchive), (batches) => { restore = batches; });
       if (!archived) return;
@@ -3498,7 +3549,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
         setConversationEmails([]);
       }
 
-      toastWithUndo(t('mail_list_extra.archived'), undoMoveAction(client, restore, undo));
+      toastWithUndo(t('mail_list_extra.archived'), undoMoveAction(client, restore, undo, undefined, reopen));
       void refreshMailboxes();
     } catch (error) {
       console.error("Failed to archive email:", error);
@@ -4594,8 +4645,8 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
 
   // Mountain View reads a message inside its conversation, as Gmail does: load
   // the rest of the thread (list properties only) whenever another opens.
-  const mvConversationThreadId = mvConversationView && !cursorOnly ? (selectedEmail?.threadId ?? null) : null;
-  const mvConversationRef = mvConversationView && !cursorOnly ? selectedEmail : null;
+  const mvConversationThreadId = readerConversationView && !cursorOnly ? (selectedEmail?.threadId ?? null) : null;
+  const mvConversationRef = readerConversationView && !cursorOnly ? selectedEmail : null;
   const mvConversationRoute = (ref: Email, fallback: NonNullable<typeof client>) => {
     const source = resolveEmailBlobContext(ref, fallback);
     return { threadClient: source.client, accountId: source.accountId };
@@ -4902,7 +4953,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     // hand) and let the body follow; the viewer shows a row without body
     // values as loading. Mountain View shows the message inside its
     // conversation, which is fetched alongside, so it waits for both.
-    const rowEmail = !mvConversationView && listEmail && 'receivedAt' in listEmail ? listEmail as Email : null;
+    const rowEmail = !readerConversationView && listEmail && 'receivedAt' in listEmail ? listEmail as Email : null;
     if (rowEmail) {
       beginOpenEmail(rowEmail);
     } else {
@@ -4931,7 +4982,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
 
       // Mountain View shows the message inside its conversation: fetch that
       // alongside the message, so the two appear together. (#1223)
-      const conversationPrefetch = mvConversationView && listEmail?.id && listEmail.threadId
+      const conversationPrefetch = readerConversationView && listEmail?.id && listEmail.threadId
         ? loadMvConversation(listEmail as Email, client)
         : null;
       // The request a mouse press on the row already started, if any.
@@ -4994,6 +5045,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
   };
 
   pluginOpenEmailRef.current = handleEmailSelect;
+  reopenEmailRef.current = handleEmailSelect;
 
   // Handle back navigation from viewer on mobile.
   // Reset to list state directly. We can't just call window.history.back()
@@ -5765,6 +5817,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
                   }, { pane: targetPane, reuseReader: hasSplit });
                 })}
                 onOpenConversation={handleOpenConversation}
+                conversationInReader={paneConversationView}
                 // Context menu handlers
                 onReply={(email) => {
                   selectEmail(email);
@@ -6052,7 +6105,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
                         // Marking the open message unread returns to the list
                         // (Gmail-style, gated on returnToListAfterAction). Staying
                         // in the reading pane would just re-mark it read on view.
-                        if (!read && useSettingsStore.getState().returnToListAfterAction) {
+                        if (!read && returnsToList()) {
                           handleMobileBack();
                         }
                       }
@@ -6069,16 +6122,17 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
                       total: Math.max(activeEmails.length, mailboxes.find((mb) => mb.id === selectedMailbox)?.totalEmails ?? (isUnifiedView ? listQueryTotal : 0)),
                     } : undefined}
                     mvFolderName={mvShell && !isScheduledView && !isUnifiedView ? currentMailboxName : undefined}
-                    mvConversation={mvConversationView ? mvConversation ?? undefined : undefined}
-                    mvConversationPending={mvConversationView && !!selectedEmail && mvConversationLoading === selectedEmail.threadId}
-                    onLoadConversationEmail={mvConversationView ? (e) => void handleLoadConversationEmail(e) : undefined}
-                    onMarkConversationEmailRead={mvConversationView ? (e) => void handleMarkConversationEmailRead(e) : undefined}
-                    onReplyConversationEmail={mvConversationView ? async (e) => {
+                    mvConversation={readerConversationView ? mvConversation ?? undefined : undefined}
+                    conversationPane={paneConversationView}
+                    mvConversationPending={readerConversationView && !!selectedEmail && mvConversationLoading === selectedEmail.threadId}
+                    onLoadConversationEmail={readerConversationView ? (e) => void handleLoadConversationEmail(e) : undefined}
+                    onMarkConversationEmailRead={readerConversationView ? (e) => void handleMarkConversationEmailRead(e) : undefined}
+                    onReplyConversationEmail={readerConversationView ? async (e) => {
                       // The reply quotes the message, so it needs the body.
                       const full = e.bodyValues ? e : await handleLoadConversationEmail(e);
                       await handleConversationReply(full ?? e);
                     } : undefined}
-                    onReplyAllConversationEmail={mvConversationView ? async (e) => {
+                    onReplyAllConversationEmail={readerConversationView ? async (e) => {
                       const full = e.bodyValues ? e : await handleLoadConversationEmail(e);
                       await handleConversationReplyAll(full ?? e);
                     } : undefined}
diff --git a/components/settings/accessibility-settings.tsx b/components/settings/accessibility-settings.tsx
index 3f6f606e2..515d9ea2e 100644
--- a/components/settings/accessibility-settings.tsx
+++ b/components/settings/accessibility-settings.tsx
@@ -12,6 +12,7 @@ import { useNoThirdPartyTraffic } from '@/hooks/use-third-party-mode';
 import { openKeyboardShortcuts } from '@/lib/app-commands';
 import { voicesForLocale } from '@/lib/read-aloud';
 import { useSpeechVoices } from '@/hooks/use-read-aloud';
+import { useReturnToListAfterAction } from '@/hooks/use-return-to-list';
 import { NOTIFICATION_SOUNDS, playNotificationSound, type NotificationSoundChoice } from '@/lib/notification-sound';
 import {
   ACCESSIBILITY_KEYS,
@@ -73,6 +74,8 @@ export function AccessibilitySettings() {
   const [resetDone, setResetDone] = useState(false);
   const locale = useLocale();
   const speechVoices = useSpeechVoices();
+  // As it applies in this layout: left alone, it follows the layout.
+  const returnToList = useReturnToListAfterAction();
 
   const toastMin = getRestriction('toastDuration')?.min;
   const allowsValue = (key: string, value: unknown) =>
@@ -502,7 +505,7 @@ export function AccessibilitySettings() {
           </SettingItem>
         )}
         <SettingItem label={tEmail('return_to_list_after_action.label')} description={tEmail('return_to_list_after_action.description')}>
-          <ToggleSwitch checked={settings.returnToListAfterAction} onChange={(checked) => set('returnToListAfterAction', checked)} />
+          <ToggleSwitch checked={returnToList.checked} onChange={(checked) => set('returnToListAfterAction', checked)} />
         </SettingItem>
       </SettingsSection>
 
diff --git a/components/settings/reading-settings.tsx b/components/settings/reading-settings.tsx
index 0b5cf8222..3f9518ce5 100644
--- a/components/settings/reading-settings.tsx
+++ b/components/settings/reading-settings.tsx
@@ -11,6 +11,7 @@ import { usePolicyStore } from '@/stores/policy-store';
 import { useContactStore } from '@/stores/contact-store';
 import { useAuthStore } from '@/stores/auth-store';
 import { useRemoteContentBlockedByOrg } from '@/hooks/use-third-party-mode';
+import { useReturnToListAfterAction } from '@/hooks/use-return-to-list';
 
 /**
  * The Reading page: the open message. Opening it, how its body is drawn,
@@ -26,12 +27,14 @@ export function ReadingSettings() {
   const tLock = useTranslations('remote_content_lock');
   const t = useTranslations('settings.email_behavior');
   const tPage = useTranslations('settings.reading_page');
+  const tPane = useTranslations('conversation_pane');
+  // As it applies in this layout: left alone, it follows the layout.
+  const returnToList = useReturnToListAfterAction();
   const [showTrustedModal, setShowTrustedModal] = useState(false);
   const { isSettingLocked, isSettingHidden, isFeatureEnabled } = usePolicyStore();
 
   const {
     markAsReadDelay,
-    returnToListAfterAction,
     mailAttachmentAction,
     attachmentPosition,
     hideInlineImageAttachments,
@@ -78,9 +81,14 @@ export function ReadingSettings() {
         </SettingItem>
         )}
 
-        <SettingItem label={t('return_to_list_after_action.label')} description={t('return_to_list_after_action.description')}>
+        <SettingItem
+          label={t('return_to_list_after_action.label')}
+          description={returnToList.followsLayout
+            ? `${t('return_to_list_after_action.description')} ${tPane('return_to_list_follows_layout')}`
+            : t('return_to_list_after_action.description')}
+        >
           <ToggleSwitch
-            checked={returnToListAfterAction}
+            checked={returnToList.checked}
             onChange={(checked) => updateSetting('returnToListAfterAction', checked)}
           />
         </SettingItem>
diff --git a/hooks/use-return-to-list.ts b/hooks/use-return-to-list.ts
new file mode 100644
index 000000000..321dfeee0
--- /dev/null
+++ b/hooks/use-return-to-list.ts
@@ -0,0 +1,28 @@
+"use client";
+
+import { useSettingsStore } from "@/stores/settings-store";
+import { usePolicyStore } from "@/stores/policy-store";
+import { useDeviceDetection } from "@/hooks/use-media-query";
+import { effectiveReturnToList, listBesideReader, returnToListSetByPolicy } from "@/lib/return-to-list";
+
+/**
+ * The "Return to list after…" switch as it applies on this device and in this
+ * layout (lib/return-to-list), and whether that comes from the layout because
+ * nobody has set it yet.
+ */
+export function useReturnToListAfterAction(): { checked: boolean; followsLayout: boolean } {
+  const { isMobile, isTablet } = useDeviceDetection();
+  const value = useSettingsStore((s) => s.returnToListAfterAction);
+  const explicitSettings = useSettingsStore((s) => s.explicitSettings);
+  const mailLayout = useSettingsStore((s) => s.mailLayout);
+  const interfaceLayout = useSettingsStore((s) => s.interfaceLayout);
+  const simpleMode = useSettingsStore((s) => s.simpleMode);
+  // Re-read when the policy arrives or changes.
+  usePolicyStore((s) => s.policy);
+  const policySet = returnToListSetByPolicy();
+  const besideReader = listBesideReader({ mailLayout, interfaceLayout, simpleMode, isMobile, isTablet });
+  return {
+    checked: effectiveReturnToList({ returnToListAfterAction: value, explicitSettings }, besideReader, policySet),
+    followsLayout: !policySet && !explicitSettings.includes("returnToListAfterAction"),
+  };
+}
diff --git a/lib/__tests__/list-step.test.ts b/lib/__tests__/list-step.test.ts
new file mode 100644
index 000000000..3445df2b7
--- /dev/null
+++ b/lib/__tests__/list-step.test.ts
@@ -0,0 +1,34 @@
+import { describe, it, expect } from 'vitest';
+import type { Email } from '@/lib/jmap/types';
+import { stepListEmail } from '../list-step';
+
+const mail = (id: string) => ({ id, threadId: `t-${id}` }) as Email;
+const emails = [mail('a'), mail('b'), mail('c'), mail('d')];
+const ids = (e: Email | null) => e?.id ?? null;
+
+describe('stepListEmail', () => {
+  it('goes on from the given message', () => {
+    expect(ids(stepListEmail(emails, 'c', 1))).toBe('d');
+    expect(ids(stepListEmail(emails, 'c', -1))).toBe('b');
+  });
+  it('stays put at either end', () => {
+    expect(ids(stepListEmail(emails, 'd', 1))).toBe('d');
+    expect(ids(stepListEmail(emails, 'a', -1))).toBe('a');
+  });
+  it('starts at the top for j and the bottom for k without a place', () => {
+    expect(ids(stepListEmail(emails, null, 1))).toBe('a');
+    expect(ids(stepListEmail(emails, null, -1))).toBe('d');
+    expect(ids(stepListEmail(emails, 'gone', 1))).toBe('a');
+  });
+  it('counts a conversation once and opens it at its row', () => {
+    // b's row stands for b and a (its older message); then d, then c.
+    const rows = [{ key: 'b', members: ['b', 'a'] }, { key: 'd', members: ['d'] }, { key: 'c', members: ['c'] }];
+    expect(ids(stepListEmail(emails, 'a', 1, rows))).toBe('d');
+    expect(ids(stepListEmail(emails, 'd', 1, rows))).toBe('c');
+    expect(ids(stepListEmail(emails, 'd', -1, rows))).toBe('b');
+    expect(ids(stepListEmail(emails, null, -1, rows))).toBe('c');
+  });
+  it('is empty for an empty list', () => {
+    expect(stepListEmail([], 'a', 1)).toBeNull();
+  });
+});
diff --git a/lib/__tests__/return-to-list.test.ts b/lib/__tests__/return-to-list.test.ts
new file mode 100644
index 000000000..a19b16d2b
--- /dev/null
+++ b/lib/__tests__/return-to-list.test.ts
@@ -0,0 +1,41 @@
+import { describe, it, expect } from 'vitest';
+import { effectiveReturnToList, listBesideReader } from '../return-to-list';
+
+// "Return to list after…": left alone it follows the layout (next message
+// with the list beside the reader, back to the list elsewhere); set by the
+// user or the admin, it decides everywhere.
+
+const untouched = { returnToListAfterAction: true, explicitSettings: [] as string[] };
+const chosen = (value: boolean) => ({ returnToListAfterAction: value, explicitSettings: ['returnToListAfterAction'] });
+
+describe('listBesideReader', () => {
+  const desktop = { isMobile: false, isTablet: false, interfaceLayout: 'default' as const };
+  it('is true for the split and horizontal layouts on a desktop', () => {
+    expect(listBesideReader({ ...desktop, mailLayout: 'split' })).toBe(true);
+    expect(listBesideReader({ ...desktop, mailLayout: 'horizontal' })).toBe(true);
+  });
+  it('is false where the message takes the list’s place', () => {
+    expect(listBesideReader({ ...desktop, mailLayout: 'focus' })).toBe(false);
+    expect(listBesideReader({ ...desktop, mailLayout: 'split', interfaceLayout: 'mountain-view' })).toBe(false);
+    expect(listBesideReader({ ...desktop, mailLayout: 'split', simpleMode: true })).toBe(false);
+    expect(listBesideReader({ ...desktop, mailLayout: 'split', isMobile: true })).toBe(false);
+    expect(listBesideReader({ ...desktop, mailLayout: 'split', isTablet: true })).toBe(false);
+  });
+});
+
+describe('effectiveReturnToList', () => {
+  it('opens the next message beside the reader while nobody set it', () => {
+    expect(effectiveReturnToList(untouched, true, false)).toBe(false);
+  });
+  it('goes back to the list elsewhere while nobody set it', () => {
+    expect(effectiveReturnToList(untouched, false, false)).toBe(true);
+  });
+  it('follows the user’s choice on every layout', () => {
+    expect(effectiveReturnToList(chosen(true), true, false)).toBe(true);
+    expect(effectiveReturnToList(chosen(false), false, false)).toBe(false);
+  });
+  it('follows an admin preset or lock', () => {
+    expect(effectiveReturnToList(untouched, true, true)).toBe(true);
+    expect(effectiveReturnToList({ ...untouched, returnToListAfterAction: false }, false, true)).toBe(false);
+  });
+});
diff --git a/lib/email-action-toast.ts b/lib/email-action-toast.ts
index 663a3b417..02d987771 100644
--- a/lib/email-action-toast.ts
+++ b/lib/email-action-toast.ts
@@ -166,13 +166,14 @@ export async function setSelectionTagWithUndo(
  *
  * `receipts` (filled while the move runs) name the messages it took to
  * another account: Undo moves those back, the same way, into the folders
- * their restore points name (undoMove).
+ * their restore points name (undoMove). `onUndone` runs once they are back.
  */
 export function undoMoveAction(
   client: IJMAPClient | null | undefined,
   batches: EmailRestoreBatch[] | null | undefined,
   labels: UndoLabels,
   receipts?: CrossAccountMoveReceipt[],
+  onUndone?: () => void,
 ): UndoToastAction | undefined {
   if (!client || !batches || !batches.some(b => b.points.length > 0)) return undefined;
   return {
@@ -183,6 +184,7 @@ export function undoMoveAction(
         try {
           await useEmailStore.getState().undoMove(client, batches, receipts ?? []);
           toast.success(labels.done);
+          onUndone?.();
         } catch (error) {
           console.error("Failed to undo:", error);
           toast.error(labels.failed);
diff --git a/lib/list-step.ts b/lib/list-step.ts
new file mode 100644
index 000000000..738b5194c
--- /dev/null
+++ b/lib/list-step.ts
@@ -0,0 +1,39 @@
+import type { Email } from '@/lib/jmap/types';
+import { emailKeyFor } from '@/lib/thread-utils';
+
+/** One row of the message list: its own key and the keys it stands for. */
+export interface ListStepRow {
+  key: string;
+  members: string[];
+}
+
+/**
+ * The message j / k open: the one after (`direction` 1) or before (-1) the
+ * message `fromKey` names, staying put at either end. `fromKey` is the open
+ * message, or the last one opened when the reader was closed, so j after
+ * Escape goes on from there. Without a place in the list, j starts at the
+ * top and k at the bottom.
+ *
+ * With `rows` (the list's rows in screen order) a conversation counts once,
+ * and opens at its newest message, as a click on its row does: the reading
+ * pane shows the rest of it.
+ */
+export function stepListEmail(
+  emails: readonly Email[],
+  fromKey: string | null | undefined,
+  direction: 1 | -1,
+  rows?: readonly ListStepRow[] | null,
+): Email | null {
+  const byKey = new Map(emails.map((e) => [emailKeyFor(e), e] as const));
+  const order: readonly ListStepRow[] = rows && rows.length > 0
+    ? rows.filter((row) => byKey.has(row.key))
+    : emails.map((e) => ({ key: emailKeyFor(e), members: [] }));
+  if (order.length === 0) return null;
+  const at = fromKey
+    ? order.findIndex((row) => row.key === fromKey || row.members.includes(fromKey))
+    : -1;
+  const target = at < 0
+    ? (direction === 1 ? 0 : order.length - 1)
+    : Math.min(order.length - 1, Math.max(0, at + direction));
+  return byKey.get(order[target].key) ?? null;
+}
diff --git a/lib/return-to-list.ts b/lib/return-to-list.ts
new file mode 100644
index 000000000..f33055bcb
--- /dev/null
+++ b/lib/return-to-list.ts
@@ -0,0 +1,50 @@
+import { effectiveMailLayout, useSettingsStore, type InterfaceLayout, type MailLayout } from '@/stores/settings-store';
+import { usePolicyStore } from '@/stores/policy-store';
+
+const KEY = 'returnToListAfterAction';
+
+/**
+ * Whether the message list and the reading pane are on screen side by side:
+ * the split and horizontal layouts on a desktop. Phones, tablets, the focused
+ * layout, Simple mode and Mountain View put the message in the list's place.
+ */
+export function listBesideReader(opts: {
+  mailLayout: MailLayout;
+  interfaceLayout: InterfaceLayout;
+  simpleMode?: boolean;
+  isMobile: boolean;
+  isTablet: boolean;
+}): boolean {
+  if (opts.isMobile || opts.isTablet) return false;
+  return effectiveMailLayout(opts.mailLayout, opts.interfaceLayout, opts.simpleMode) !== 'focus';
+}
+
+/**
+ * "Return to list after delete, archive, move or mark unread", as it applies
+ * here. Set by the user (on any device: the choice syncs) or by the admin
+ * policy, the setting decides. Left alone, it follows the layout: with the
+ * list beside the reading pane the next message opens, as in Outlook, so a
+ * folder is worked through with e, e, e; where the message takes the list's
+ * place it goes back to the list. Each device judges its own layout.
+ */
+export function effectiveReturnToList(
+  settings: { returnToListAfterAction: boolean; explicitSettings: readonly string[] },
+  besideReader: boolean,
+  policySet: boolean,
+): boolean {
+  if (policySet || settings.explicitSettings.includes(KEY)) return settings.returnToListAfterAction;
+  return besideReader ? false : settings.returnToListAfterAction;
+}
+
+/** Whether the admin policy presets or locks the setting. */
+export function returnToListSetByPolicy(): boolean {
+  const policy = usePolicyStore.getState();
+  const defaults = policy.policy?.defaults;
+  return (!!defaults && Object.prototype.hasOwnProperty.call(defaults, KEY)) || policy.isSettingLocked(KEY);
+}
+
+/** The setting as it applies now, read at the moment of the action. */
+export function returnToListAfterAction(besideReader: boolean): boolean {
+  return effectiveReturnToList(useSettingsStore.getState(), besideReader, returnToListSetByPolicy());
+}
+
diff --git a/locales/ar/common.json b/locales/ar/common.json
index 17e6a0535..f7c9d0564 100644
--- a/locales/ar/common.json
+++ b/locales/ar/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "توسيع المحادثة: {subject}",
     "collapse_named": "طي المحادثة: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, zero {عرض # رسالة أقدم} one {عرض رسالة أقدم واحدة} two {عرض رسالتين أقدم} few {عرض # رسائل أقدم} many {عرض # رسالة أقدم} other {عرض # رسالة أقدم}}",
+    "return_to_list_follows_layout": "ما لم تغيّره، يتبع هذا التخطيط: متوقف عندما تكون القائمة والرسالة جنبًا إلى جنب، ومفعّل في غير ذلك."
+  },
   "identities": {
     "modal_title": "إدارة هويات الإرسال",
     "create_new": "إنشاء هوية جديدة",
diff --git a/locales/ca/common.json b/locales/ca/common.json
index c7b1f4f7e..f70c3e5cf 100644
--- a/locales/ca/common.json
+++ b/locales/ca/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Desplega la conversa: {subject}",
     "collapse_named": "Replega la conversa: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Mostra # missatge anterior} other {Mostra # missatges anteriors}}",
+    "return_to_list_follows_layout": "Mentre no ho canviïs, segueix el disseny: desactivat quan la llista i el missatge són l'un al costat de l'altre, activat en els altres casos."
+  },
   "identities": {
     "modal_title": "Gestiona les identitats d'enviament",
     "create_new": "Crea una identitat nova",
diff --git a/locales/cs/common.json b/locales/cs/common.json
index f1425e905..a642b2368 100644
--- a/locales/cs/common.json
+++ b/locales/cs/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Rozbalit konverzaci: {subject}",
     "collapse_named": "Sbalit konverzaci: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Zobrazit # starší zprávu} few {Zobrazit # starší zprávy} many {Zobrazit # starší zprávy} other {Zobrazit # starších zpráv}}",
+    "return_to_list_follows_layout": "Dokud to nezměníte, řídí se to rozvržením: vypnuto, když jsou seznam a zpráva vedle sebe, jinak zapnuto."
+  },
   "identities": {
     "modal_title": "Správa identit odesílatele",
     "create_new": "Vytvořit novou identitu",
diff --git a/locales/da/common.json b/locales/da/common.json
index 352ce130d..136421edb 100644
--- a/locales/da/common.json
+++ b/locales/da/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Udvid samtale: {subject}",
     "collapse_named": "Skjul samtale: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Vis # ældre besked} other {Vis # ældre beskeder}}",
+    "return_to_list_follows_layout": "Indtil du ændrer det, følger det layoutet: fra, når listen og beskeden står side om side, ellers til."
+  },
   "identities": {
     "modal_title": "Administrér afsenderidentiteter",
     "create_new": "Opret ny identitet",
diff --git a/locales/de/common.json b/locales/de/common.json
index 6bf94c958..fe7182ed4 100644
--- a/locales/de/common.json
+++ b/locales/de/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Konversation aufklappen: {subject}",
     "collapse_named": "Konversation zuklappen: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {# ältere Nachricht anzeigen} other {# ältere Nachrichten anzeigen}}",
+    "return_to_list_follows_layout": "Solange Sie es nicht ändern, richtet sich das nach dem Layout: aus, wenn Liste und Nachricht nebeneinander stehen, sonst an."
+  },
   "identities": {
     "modal_title": "Sendeidentitäten verwalten",
     "create_new": "Neue Identität erstellen",
diff --git a/locales/en/common.json b/locales/en/common.json
index 4d35cc577..b9eaf1002 100644
--- a/locales/en/common.json
+++ b/locales/en/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Expand conversation: {subject}",
     "collapse_named": "Collapse conversation: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Show # older message} other {Show # older messages}}",
+    "return_to_list_follows_layout": "Until you change it, this follows the layout: off when the list and the message are side by side, on otherwise."
+  },
   "identities": {
     "modal_title": "Manage sending identities",
     "create_new": "New identity",
diff --git a/locales/es/common.json b/locales/es/common.json
index 4d8046bab..0d961ed52 100644
--- a/locales/es/common.json
+++ b/locales/es/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Expandir conversación: {subject}",
     "collapse_named": "Contraer conversación: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Mostrar # mensaje anterior} other {Mostrar # mensajes anteriores}}",
+    "return_to_list_follows_layout": "Mientras no lo cambies, sigue el diseño: desactivado cuando la lista y el mensaje están uno al lado del otro, activado en los demás casos."
+  },
   "identities": {
     "modal_title": "Administrar Identidades de Envío",
     "create_new": "Crear Nueva Identidad",
diff --git a/locales/et/common.json b/locales/et/common.json
index 82a04231e..e249abb6c 100644
--- a/locales/et/common.json
+++ b/locales/et/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Ava vestlus: {subject}",
     "collapse_named": "Sulge vestlus: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Näita # vanemat sõnumit} other {Näita # vanemat sõnumit}}",
+    "return_to_list_follows_layout": "Kuni te seda ei muuda, järgib see paigutust: väljas, kui loend ja sõnum on kõrvuti, muidu sees."
+  },
   "identities": {
     "modal_title": "Halda saatja identiteete",
     "create_new": "Loo uus identiteet",
diff --git a/locales/fa/common.json b/locales/fa/common.json
index f8e80ab74..ae98f8257 100644
--- a/locales/fa/common.json
+++ b/locales/fa/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "باز کردن مکالمه: {subject}",
     "collapse_named": "جمع کردن مکالمه: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {نمایش # پیام قدیمی‌تر} other {نمایش # پیام قدیمی‌تر}}",
+    "return_to_list_follows_layout": "تا وقتی آن را تغییر ندهید، از چیدمان پیروی می‌کند: وقتی فهرست و پیام کنار هم هستند خاموش، در غیر این صورت روشن."
+  },
   "identities": {
     "modal_title": "مدیریت هویت‌های ارسال",
     "create_new": "ایجاد هویت جدید",
diff --git a/locales/fr/common.json b/locales/fr/common.json
index 7295c3127..71ac3ddb7 100644
--- a/locales/fr/common.json
+++ b/locales/fr/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Développer la conversation: {subject}",
     "collapse_named": "Réduire la conversation: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Afficher # message plus ancien} other {Afficher # messages plus anciens}}",
+    "return_to_list_follows_layout": "Tant que vous ne le modifiez pas, ce réglage suit la disposition : désactivé quand la liste et le message sont côte à côte, activé sinon."
+  },
   "identities": {
     "modal_title": "Gérer les identités d'envoi",
     "create_new": "Créer une nouvelle identité",
diff --git a/locales/he/common.json b/locales/he/common.json
index c3fac8aa4..5f5a17909 100644
--- a/locales/he/common.json
+++ b/locales/he/common.json
@@ -3687,6 +3687,10 @@
     "expand_named": "הרחב את השיחה: {subject}",
     "collapse_named": "כווץ את השיחה: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {הצגת הודעה ישנה אחת} two {הצגת שתי הודעות ישנות} other {הצגת # הודעות ישנות}}",
+    "return_to_list_follows_layout": "כל עוד לא תשנו זאת, זה נקבע לפי הפריסה: כבוי כשהרשימה וההודעה זו לצד זו, ופועל בכל מצב אחר."
+  },
   "identities": {
     "modal_title": "ניהול זהויות שליחה",
     "create_new": "צור זהות חדשה",
diff --git a/locales/hu/common.json b/locales/hu/common.json
index acb38477f..90ca815c8 100644
--- a/locales/hu/common.json
+++ b/locales/hu/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Beszélgetés kibontása: {subject}",
     "collapse_named": "Beszélgetés összecsukása: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {# régebbi üzenet megjelenítése} other {# régebbi üzenet megjelenítése}}",
+    "return_to_list_follows_layout": "Amíg nem módosítja, az elrendezést követi: ki van kapcsolva, ha a lista és az üzenet egymás mellett van, egyébként be."
+  },
   "identities": {
     "modal_title": "Küldő azonosságok kezelése",
     "create_new": "Új azonosság létrehozása",
diff --git a/locales/it/common.json b/locales/it/common.json
index 085d85039..88c81d14e 100644
--- a/locales/it/common.json
+++ b/locales/it/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Espandi conversazione: {subject}",
     "collapse_named": "Comprimi conversazione: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Mostra # messaggio precedente} other {Mostra # messaggi precedenti}}",
+    "return_to_list_follows_layout": "Finché non lo modifichi, segue il layout: disattivato quando l'elenco e il messaggio sono affiancati, attivato negli altri casi."
+  },
   "identities": {
     "modal_title": "Gestisci identità di invio",
     "create_new": "Crea nuova identità",
diff --git a/locales/ja/common.json b/locales/ja/common.json
index e1687db7f..f5e526756 100644
--- a/locales/ja/common.json
+++ b/locales/ja/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "会話を展開: {subject}",
     "collapse_named": "会話を折りたたむ: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, other {以前のメッセージを # 件表示}}",
+    "return_to_list_follows_layout": "変更するまでは、レイアウトに合わせて切り替わります。一覧とメッセージが横に並ぶ場合はオフ、それ以外はオンです。"
+  },
   "identities": {
     "modal_title": "送信者情報を管理",
     "create_new": "新しい送信者情報を作成",
diff --git a/locales/ko/common.json b/locales/ko/common.json
index 5e7002cc8..7f331e371 100644
--- a/locales/ko/common.json
+++ b/locales/ko/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "대화 펼치기: {subject}",
     "collapse_named": "대화 접기: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, other {이전 메시지 #개 보기}}",
+    "return_to_list_follows_layout": "변경하기 전까지는 레이아웃을 따릅니다. 목록과 메시지가 나란히 있으면 꺼지고, 그 밖에는 켜집니다."
+  },
   "identities": {
     "modal_title": "보내는 사람 관리",
     "create_new": "새 보내는 사람 추가",
diff --git a/locales/lv/common.json b/locales/lv/common.json
index fc32baa3c..5a3041639 100644
--- a/locales/lv/common.json
+++ b/locales/lv/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Izvērst sarunu: {subject}",
     "collapse_named": "Sairt sarunu: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, zero {Rādīt # vecākas ziņas} one {Rādīt # vecāku ziņu} other {Rādīt # vecākas ziņas}}",
+    "return_to_list_follows_layout": "Kamēr to nemaināt, tas seko izkārtojumam: izslēgts, ja saraksts un ziņa ir blakus, citādi ieslēgts."
+  },
   "identities": {
     "modal_title": "Pārvaldīt sūtītāja identitātes",
     "create_new": "Izveidot jaunu identitāti",
diff --git a/locales/mn/common.json b/locales/mn/common.json
index e045789d9..e091a4658 100644
--- a/locales/mn/common.json
+++ b/locales/mn/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Харилцан яриаг өргөжүүлэх: {subject}",
     "collapse_named": "Харилцан яриаг хураах: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Өмнөх # захиа харуулах} other {Өмнөх # захиа харуулах}}",
+    "return_to_list_follows_layout": "Та өөрчлөхөөс нааш энэ нь байрлалаас хамаарна: жагсаалт ба захиа зэрэгцэн байвал унтраалттай, бусад үед асаалттай."
+  },
   "identities": {
     "modal_title": "Илгээж буй таниулбаруудыг удирдах",
     "create_new": "Шинэ таниулбар үүсгэх",
diff --git a/locales/nb/common.json b/locales/nb/common.json
index 4991e10b6..d10b88cc3 100644
--- a/locales/nb/common.json
+++ b/locales/nb/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Utvid samtalen: {subject}",
     "collapse_named": "Fold sammen samtalen: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Vis # eldre melding} other {Vis # eldre meldinger}}",
+    "return_to_list_follows_layout": "Inntil du endrer det, følger det oppsettet: av når listen og meldingen står side om side, ellers på."
+  },
   "identities": {
     "modal_title": "Administrer avsenderidentiteter",
     "create_new": "Opprett ny identitet",
diff --git a/locales/nl/common.json b/locales/nl/common.json
index 658ced16e..f2304f1a9 100644
--- a/locales/nl/common.json
+++ b/locales/nl/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Gesprek uitklappen: {subject}",
     "collapse_named": "Gesprek inklappen: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {# ouder bericht tonen} other {# oudere berichten tonen}}",
+    "return_to_list_follows_layout": "Zolang je het niet wijzigt, volgt dit de indeling: uit als de lijst en het bericht naast elkaar staan, anders aan."
+  },
   "identities": {
     "modal_title": "Verzendidentiteiten beheren",
     "create_new": "Nieuwe identiteit aanmaken",
diff --git a/locales/pl/common.json b/locales/pl/common.json
index 82d94a25f..2a29da700 100644
--- a/locales/pl/common.json
+++ b/locales/pl/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Rozwiń konwersację: {subject}",
     "collapse_named": "Zwiń konwersację: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Pokaż # starszą wiadomość} few {Pokaż # starsze wiadomości} many {Pokaż # starszych wiadomości} other {Pokaż # starszej wiadomości}}",
+    "return_to_list_follows_layout": "Dopóki tego nie zmienisz, ustawienie zależy od układu: wyłączone, gdy lista i wiadomość są obok siebie, w innych przypadkach włączone."
+  },
   "identities": {
     "modal_title": "Zarządzaj tożsamościami nadawcy",
     "create_new": "Utwórz nową tożsamość",
diff --git a/locales/pt/common.json b/locales/pt/common.json
index b5fc8675c..05686236e 100644
--- a/locales/pt/common.json
+++ b/locales/pt/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Expandir conversa: {subject}",
     "collapse_named": "Recolher conversa: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Mostrar # mensagem anterior} other {Mostrar # mensagens anteriores}}",
+    "return_to_list_follows_layout": "Enquanto não alterar, segue o layout: desligado quando a lista e a mensagem estão lado a lado, ligado nos outros casos."
+  },
   "identities": {
     "modal_title": "Gerenciar Identidades de Envio",
     "create_new": "Criar Nova Identidade",
diff --git a/locales/ro/common.json b/locales/ro/common.json
index ffee770f9..f73bcc5ee 100644
--- a/locales/ro/common.json
+++ b/locales/ro/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Extinde conversația: {subject}",
     "collapse_named": "Ascunde conversația: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Afișează # mesaj mai vechi} few {Afișează # mesaje mai vechi} other {Afișează # de mesaje mai vechi}}",
+    "return_to_list_follows_layout": "Cât timp nu îl modificați, urmează aspectul: dezactivat când lista și mesajul sunt unul lângă altul, activat în rest."
+  },
   "identities": {
     "modal_title": "Gestionarea identităților de expediere",
     "create_new": "Creați o identitate nouă",
diff --git a/locales/ru/common.json b/locales/ru/common.json
index 7de1300e5..415524f9c 100644
--- a/locales/ru/common.json
+++ b/locales/ru/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Развернуть разговор: {subject}",
     "collapse_named": "Свернуть разговор: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Показать # более раннее письмо} few {Показать # более ранних письма} many {Показать # более ранних писем} other {Показать # более раннего письма}}",
+    "return_to_list_follows_layout": "Пока вы это не измените, настройка зависит от макета: выключена, когда список и письмо стоят рядом, в остальных случаях включена."
+  },
   "identities": {
     "modal_title": "Управление идентификациями отправителя",
     "create_new": "Создать новую идентификацию",
diff --git a/locales/sk/common.json b/locales/sk/common.json
index 430a9f3da..f7ffabee1 100644
--- a/locales/sk/common.json
+++ b/locales/sk/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Rozbaliť konverzáciu: {subject}",
     "collapse_named": "Zbaliť konverzáciu: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Zobraziť # staršiu správu} few {Zobraziť # staršie správy} many {Zobraziť # staršej správy} other {Zobraziť # starších správ}}",
+    "return_to_list_follows_layout": "Kým to nezmeníte, riadi sa to rozložením: vypnuté, keď sú zoznam a správa vedľa seba, inak zapnuté."
+  },
   "identities": {
     "modal_title": "Správa identít odosielateľa",
     "create_new": "Vytvoriť novú identitu",
diff --git a/locales/th/common.json b/locales/th/common.json
index c33fb8a6d..614aff1eb 100644
--- a/locales/th/common.json
+++ b/locales/th/common.json
@@ -621,6 +621,10 @@
     "expand_named": "ขยายการสนทนา: {subject}",
     "collapse_named": "ย่อการสนทนา: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, other {แสดงข้อความก่อนหน้า # ฉบับ}}",
+    "return_to_list_follows_layout": "จนกว่าคุณจะเปลี่ยน ค่านี้จะเป็นไปตามเลย์เอาต์: ปิดเมื่อรายการและข้อความอยู่เคียงข้างกัน และเปิดในกรณีอื่น"
+  },
   "notifications": {
     "email_sent": "ส่งอีเมลแล้ว",
     "email_deleted": "ลบอีเมลแล้ว",
diff --git a/locales/tr/common.json b/locales/tr/common.json
index 896667e5a..034e7fb64 100644
--- a/locales/tr/common.json
+++ b/locales/tr/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Konuşmayı genişlet: {subject}",
     "collapse_named": "Konuşmayı daralt: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {# eski iletiyi göster} other {# eski iletiyi göster}}",
+    "return_to_list_follows_layout": "Siz değiştirene kadar bu ayar düzene göre belirlenir: liste ve ileti yan yanaysa kapalı, değilse açık."
+  },
   "identities": {
     "modal_title": "Gönderme Kimliklerini Yönet",
     "create_new": "Yeni Kimlik Oluştur",
diff --git a/locales/uk/common.json b/locales/uk/common.json
index 6eb158f70..59d9b036c 100644
--- a/locales/uk/common.json
+++ b/locales/uk/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "Розгорнути бесіду: {subject}",
     "collapse_named": "Згорнути бесіду: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, one {Показати # давніший лист} few {Показати # давніші листи} many {Показати # давніших листів} other {Показати # давнішого листа}}",
+    "return_to_list_follows_layout": "Поки ви це не зміните, налаштування залежить від макета: вимкнено, коли список і лист розташовані поруч, в інших випадках увімкнено."
+  },
   "identities": {
     "modal_title": "Керування ідентифікаторами надсилання",
     "create_new": "Створіть нову ідентичність",
diff --git a/locales/vi/common.json b/locales/vi/common.json
index 76bee5d4c..f1ebc9ad2 100644
--- a/locales/vi/common.json
+++ b/locales/vi/common.json
@@ -3802,6 +3802,10 @@
     "expand_named": "Mở rộng cuộc trò chuyện: {subject}",
     "collapse_named": "Thu gọn cuộc trò chuyện: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, other {Hiện # thư cũ hơn}}",
+    "return_to_list_follows_layout": "Cho đến khi bạn thay đổi, cài đặt này theo bố cục: tắt khi danh sách và thư nằm cạnh nhau, bật trong các trường hợp khác."
+  },
   "identities": {
     "modal_title": "Quản lý danh tính gửi thư",
     "create_new": "Danh tính mới",
diff --git a/locales/zh-TW/common.json b/locales/zh-TW/common.json
index 0c40b5aaf..c2487087d 100644
--- a/locales/zh-TW/common.json
+++ b/locales/zh-TW/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "展開對話串: {subject}",
     "collapse_named": "收合對話串: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, other {顯示 # 封較早的郵件}}",
+    "return_to_list_follows_layout": "在您變更之前，此項會依版面配置而定：清單與郵件並排顯示時關閉，其他情況下開啟。"
+  },
   "identities": {
     "modal_title": "管理寄件身分",
     "create_new": "建立新的寄件身分",
diff --git a/locales/zh/common.json b/locales/zh/common.json
index 62424ddf5..65b4c5748 100644
--- a/locales/zh/common.json
+++ b/locales/zh/common.json
@@ -3790,6 +3790,10 @@
     "expand_named": "展开会话: {subject}",
     "collapse_named": "折叠会话: {subject}"
   },
+  "conversation_pane": {
+    "show_older": "{count, plural, other {显示 # 封较早的邮件}}",
+    "return_to_list_follows_layout": "在你更改之前，此项随布局而定：列表和邮件并排显示时关闭，其他情况下开启。"
+  },
   "identities": {
     "modal_title": "管理发送身份",
     "create_new": "创建新身份",