diff --git a/components/email/__tests__/email-list-batch-bar.test.tsx b/components/email/__tests__/email-list-batch-bar.test.tsx
index c44dc2df3..67bddb70b 100644
--- a/components/email/__tests__/email-list-batch-bar.test.tsx
+++ b/components/email/__tests__/email-list-batch-bar.test.tsx
@@ -108,6 +108,28 @@ describe('selection bar: Move, read state and the reading pane', () => {
   });
 });
 
+describe('select all in the folder (mail-p2-11)', () => {
+  it('offers the rest of the folder once every loaded row is ticked, and ticks it', async () => {
+    const third = { ...useEmailStore.getState().emails[0], id: 'three', threadId: 't-three', blobId: 'b-three' } as Email;
+    const loadMoreEmails = vi.fn(async () => {
+      useEmailStore.setState({ emails: [...useEmailStore.getState().emails, third], hasMoreEmails: false });
+    });
+    useEmailStore.setState({ hasMoreEmails: true, loadMoreEmails, totalEmails: 3 });
+    render(<EmailList emails={useEmailStore.getState().emails} />);
+    const offer = screen.getByTestId('select-all-in-view');
+    expect(offer.textContent).toBe('mail_p2_list.select_all_in_folder');
+    fireEvent.click(offer.querySelector('button')!);
+    await waitFor(() => expect([...useEmailStore.getState().selectedEmailKeys].sort()).toEqual(['one', 'three', 'two']));
+    expect(loadMoreEmails).toHaveBeenCalledTimes(1);
+  });
+
+  it('offers nothing while only some loaded rows are ticked', () => {
+    useEmailStore.setState({ hasMoreEmails: true, selectedEmailKeys: new Set(['one']) });
+    render(<EmailList emails={useEmailStore.getState().emails} />);
+    expect(screen.queryByTestId('select-all-in-view')).toBeNull();
+  });
+});
+
 describe('the reading pane for a selection (mail-p2-15)', () => {
   it('names its buttons in words, while the bar beside the list keeps icons', () => {
     const host = document.createElement('div');
diff --git a/components/email/email-list.tsx b/components/email/email-list.tsx
index de0de91fe..c8d3fa426 100644
--- a/components/email/email-list.tsx
+++ b/components/email/email-list.tsx
@@ -143,6 +143,9 @@ type ListItem =
   | { kind: 'header'; section: 'unread' | 'rest' }
   | { kind: 'unread-empty' };
 
+/** The most messages "Select all N conversations" loads to tick them (mail-p2-11). */
+const SELECT_ALL_LIMIT = 5000;
+
 /** Below this width the batch toolbar drops its labels (see batchNarrow). */
 const BATCH_TOOLBAR_WIDE = 640;
 
@@ -848,6 +851,57 @@ export function EmailList({
   const currentMailbox = mailboxes.find(m => m.id === selectedMailbox);
   const isEmptyableFolder = currentMailbox?.role === 'trash' || currentMailbox?.role === 'junk';
 
+  // Every loaded row ticked and more on the server: offer the rest, as Gmail
+  // does (mail-p2-11). Taking it loads the remaining pages and ticks them,
+  // so the batch actions, their Undo and their counts work as for any
+  // selection. At most SELECT_ALL_LIMIT messages are loaded for it.
+  const [selectingAll, setSelectingAll] = useState(false);
+  const allLoadedSelected = hasSelection && emails.length > 0 && emails.every((e) => selectedEmailKeys.has(emailKeyFor(e)));
+  const offerSelectAll = allLoadedSelected && footerHasMore && !isScheduledView && !hideBatchToolbar && !!client
+    && emails.length < SELECT_ALL_LIMIT;
+  const inPlainFolder = !!currentMailbox && !searchQuery.trim() && isFilterEmpty(searchFilters) && !isUnifiedView;
+  const viewTotal = Math.max(
+    inPlainFolder
+      ? (disableThreading ? currentMailbox.totalEmails : (currentMailbox.totalThreads || currentMailbox.totalEmails))
+      : totalEmails,
+    selectionRows + 1,
+  );
+  const selectAllLabel = inPlainFolder
+    ? tRoot(disableThreading ? 'mail_p2_list.select_all_emails_in_folder' : 'mail_p2_list.select_all_in_folder', {
+        count: viewTotal,
+        folder: localizeMailboxName(currentMailbox.role, currentMailbox.name, (k) => tSidebar(`mailboxes.${k}`)),
+      })
+    : tRoot(disableThreading ? 'mail_p2_list.select_all_emails' : 'mail_p2_list.select_all_conversations', { count: viewTotal });
+  const handleSelectAllInView = async () => {
+    if (!client || selectingAll) return;
+    const view = () => {
+      const state = useEmailStore.getState();
+      return `${state.selectedMailbox}|${state.searchQuery}|${state.isUnifiedView}|${state.unifiedRole}`;
+    };
+    const startedIn = view();
+    setSelectingAll(true);
+    try {
+      for (let pages = 0; pages < 1000; pages++) {
+        const state = useEmailStore.getState();
+        if (view() !== startedIn || state.selectedEmailKeys.size === 0) return;
+        if (!state.hasMoreEmails || state.emails.length >= SELECT_ALL_LIMIT) break;
+        if (state.isLoadingMore) {
+          await new Promise((resolve) => setTimeout(resolve, 50));
+          continue;
+        }
+        const before = state.emails.length;
+        await state.loadMoreEmails(client);
+        const after = useEmailStore.getState();
+        if (after.emails.length === before && !after.isLoadingMore) break;
+      }
+      // Another folder opened or the selection was cleared meanwhile: leave it.
+      if (view() !== startedIn || useEmailStore.getState().selectedEmailKeys.size === 0) return;
+      useEmailStore.getState().selectAllEmails();
+    } finally {
+      setSelectingAll(false);
+    }
+  };
+
   const handleEmptyFolder = async () => {
     if (!client || isProcessing || !currentMailbox) return;
 
@@ -1122,7 +1176,7 @@ export function EmailList({
         inert={!(hasSelection && !isScheduledView && !hideBatchToolbar)}
         className={cn(
           "transition-all duration-300 ease-in-out overflow-hidden",
-          hasSelection && !isScheduledView && !hideBatchToolbar ? "max-h-16 opacity-100" : "max-h-0 opacity-0"
+          hasSelection && !isScheduledView && !hideBatchToolbar ? (offerSelectAll || selectingAll ? "max-h-28 opacity-100" : "max-h-16 opacity-100") : "max-h-0 opacity-0"
         )}
       >
         {/* Only drawn while shown: collapsed it would still render every button. */}
@@ -1218,6 +1272,19 @@ export function EmailList({
           </div>
         </div>
         )}
+        {hasSelection && !isScheduledView && !hideBatchToolbar && (offerSelectAll || selectingAll) && (
+          <div className="px-4 py-1.5 border-b border-border bg-accent/20 text-center text-sm" data-testid="select-all-in-view">
+            <button
+              type="button"
+              onClick={() => void handleSelectAllInView()}
+              disabled={selectingAll}
+              aria-busy={selectingAll || undefined}
+              className="text-primary font-medium hover:underline disabled:no-underline disabled:opacity-70"
+            >
+              {selectingAll ? tRoot('mail_p2_list.selecting_all') : selectAllLabel}
+            </button>
+          </div>
+        )}
       </div>
 
       {/* Advanced Search Filter Chips */}
diff --git a/components/mail/__tests__/mail-app-list-ux.test.tsx b/components/mail/__tests__/mail-app-list-ux.test.tsx
index b209cea91..54354744c 100644
--- a/components/mail/__tests__/mail-app-list-ux.test.tsx
+++ b/components/mail/__tests__/mail-app-list-ux.test.tsx
@@ -174,6 +174,18 @@ describe('the reading pane for a selection', () => {
   });
 });
 
+describe('the list header checkbox (mail-p2-11)', () => {
+  it('ticks every loaded row on the first click and clears them on the second', () => {
+    const second = { ...message, id: 'm2', threadId: 't-m2', subject: 'm2' } as Email;
+    useEmailStore.setState({ emails: [message, second] } as never);
+    render(<MailApp />);
+    fireEvent.click(screen.getByRole('button', { name: /^email_list\.batch_actions\.select/ }));
+    expect([...useEmailStore.getState().selectedEmailKeys].sort()).toEqual(['m1', 'm2']);
+    fireEvent.click(screen.getByRole('button', { name: 'email_list.batch_actions.clear_selection' }));
+    expect(useEmailStore.getState().selectedEmailKeys.size).toBe(0);
+  });
+});
+
 describe('the new folder dialogs', () => {
   it.each([
     ['stub new folder', 'mail_list_extra.new_folder_title'],
diff --git a/components/mail/mail-app.tsx b/components/mail/mail-app.tsx
index 556e6e1d1..59c95a26f 100644
--- a/components/mail/mail-app.tsx
+++ b/components/mail/mail-app.tsx
@@ -5672,24 +5672,15 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
                   {/* Select / Select All toggle */}
                   <ToolbarButton
                     onClick={() => {
-                      if (selectedEmailKeys.size > 0) {
-                        if (selectedEmailKeys.size === activeEmails.length) {
-                          clearSelection();
-                        } else {
-                          selectAllEmails();
-                        }
-                      } else if (activeEmails.length > 0) {
-                        // The open message when it is in this list, else the
-                        // first row - as an email, so the selection is keyed by
-                        // its owning account and not by a colliding id.
-                        const openKey = selectedEmail ? emailKeyFor(selectedEmail) : null;
-                        const target = activeEmails.find((e) => emailKeyFor(e) === openKey) ?? activeEmails[0];
-                        toggleEmailSelection(target);
-                      }
+                      // One click ticks every loaded row, a second clears
+                      // them, as Gmail's box does (mail-p2-11). The bar then
+                      // offers the rest of the folder.
+                      if (selectedEmailKeys.size > 0) clearSelection();
+                      else if (activeEmails.length > 0) selectAllEmails();
                     }}
                     disabled={isScheduledView}
                     active={selectedEmailKeys.size > 0}
-                    label={selectedEmailKeys.size > 0 ? (selectedEmailKeys.size === activeEmails.length ? t('email_list.batch_actions.clear_selection') : t('email_list.batch_actions.select_all')) : t('email_list.batch_actions.select')}
+                    label={selectedEmailKeys.size > 0 ? t('email_list.batch_actions.clear_selection') : t('email_list.batch_actions.select_all')}
                     title={isScheduledView ? t('email_viewer.scheduled_actions_only') : undefined}
                   >
                     {selectedEmailKeys.size > 0 ? <CheckSquare /> : <Square />}