diff --git a/components/mail/__tests__/blob-routing.test.tsx b/components/mail/__tests__/blob-routing.test.tsx
index 668edfa81..b0777c3db 100644
--- a/components/mail/__tests__/blob-routing.test.tsx
+++ b/components/mail/__tests__/blob-routing.test.tsx
@@ -75,6 +75,8 @@ vi.mock('@/components/files/file-preview-modal', () => ({ FilePreviewModal: ({ o
 const { MailApp } = await import('../mail-app');
 const { ConversationEmailBody } = await import('@/components/email/thread-conversation-view');
 const { EmailViewer } = await import('@/components/email/email-viewer');
+const { ProEmailTabBody } = await import('@/components/pro/pro-email-tab-body');
+const { ProFolderTabBody } = await import('@/components/pro/pro-folder-tab-body');
 
 const sharedMailbox = { id: 'nrichmond:inbox', originalId: 'inbox', name: 'Shared', isShared: true, accountId: 'nrichmond' } as Mailbox;
 const primaryMailbox = { id: 'inbox', name: 'Inbox', role: 'inbox' } as Mailbox;
@@ -602,3 +604,132 @@ describe('conversation blob routing', () => {
     expect(URL.revokeObjectURL).toHaveBeenCalledWith('blob:owner-a');
   });
 });
+
+
+// Pro hosts must carry the same message-scoped context as MailApp, including
+// when the global mail selection is absent or belongs to another message.
+type ProBlobAction = 'download' | 'preview click' | 'CID' | 'export';
+const proBlobActions: ProBlobAction[] = ['download', 'preview click', 'CID', 'export'];
+const proRoutes = [
+  { label: 'direct shared folder', secondary: false, owner: 'nrichmond', selection: 'null', unified: false },
+  { label: 'secondary shared folder', secondary: true, owner: 'nrichmond', selection: 'unrelated', unified: false },
+  { label: 'primary folder', secondary: false, owner: 'postal12345', selection: 'null', unified: false },
+  { label: 'secondary primary folder', secondary: true, owner: 'secondary-primary', selection: 'unrelated', unified: false },
+  { label: 'Unified tab, null selection', secondary: true, owner: 'nrichmond', selection: 'null', unified: true },
+  { label: 'Unified tab, unrelated selection', secondary: true, owner: 'nrichmond', selection: 'unrelated', unified: true },
+  { label: 'explicit secondary email tab', secondary: true, owner: 'nrichmond', selection: 'null', unified: false, emailTab: true },
+];
+
+async function openProMessage(route: typeof proRoutes[number], action: ProBlobAction) {
+  const { a, b, fetchMock } = await conversationClients();
+  const origin = route.secondary ? b : a;
+  const full = message({
+    subject: 'Pro message',
+    attachments: [{ ...cardAttachment, name: 'photo.png', ...(action === 'CID' ? { cid: 'test-image' } : {}) }],
+    ...(action === 'CID' ? {
+      textBody: [], htmlBody: [{ partId: '1', blobId: 'html-blob', type: 'text/html', size: 30 }],
+      bodyValues: { '1': { value: '<img src="cid:test-image">', isTruncated: false, isEncodingProblem: false } },
+    } : {}),
+  });
+  const stub = { ...full, sourceClientAccountId: 'login-other', sourceAccountId: route.owner };
+  vi.spyOn(a, 'getEmail').mockResolvedValue(full);
+  vi.spyOn(b, 'getEmail').mockResolvedValue(full);
+  useSettingsStore.setState({ emailDownloadTemplate: '{subject}', mailAttachmentAction: action === 'preview click' ? 'preview' : 'download' });
+  useEmailStore.setState({
+    emails: route.unified ? [stub] : [],
+    selectedEmail: route.selection === 'null' ? null : message({ id: 'unrelated', sourceClientAccountId: 'login-primary', sourceAccountId: 'unrelated-owner' }),
+    isUnifiedView: route.unified, selectedMailbox: route.unified ? '__unified_inbox__' : sharedMailbox.id,
+    accountMailboxes: { 'login-primary': [primaryMailbox, sharedMailbox], 'login-other': [primaryMailbox, sharedMailbox] },
+  });
+  if (route.unified || route.emailTab) {
+    render(<ProEmailTabBody tabId="reader" data={{ accountId: route.owner, clientAccountId: route.emailTab ? 'login-other' : undefined, emailId: full.id, mailboxId: '__unified_inbox__', title: full.subject! }} />);
+  } else {
+    const mailbox = route.owner === 'nrichmond' ? sharedMailbox : primaryMailbox;
+    vi.spyOn(origin, 'getEmails').mockResolvedValue({ emails: [full], total: 1, hasMore: false });
+    render(<ProFolderTabBody tabId="folder" data={{ accountId: route.secondary ? 'login-other' : 'login-primary', mailboxId: mailbox.id, title: mailbox.name }} />);
+    fireEvent.click(await screen.findByText('Pro message'));
+  }
+  if (action === 'CID') await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(1));
+  else await screen.findAllByText('photo.png');
+  return { a, b, origin, fetchMock, full };
+}
+
+async function actOnProBlob(action: ProBlobAction) {
+  if (action === 'download') await downloadAttachment();
+  if (action === 'preview click') {
+    fireEvent.click((await screen.findAllByText('photo.png'))[0]);
+    // Preserve Pro's existing action: Preview clicks download, with no modal.
+    expect(screen.queryByText('Preview fetch')).not.toBeInTheDocument();
+  }
+  if (action === 'export') await exportEmail();
+}
+function expectProBlob(route: typeof proRoutes[number], action: ProBlobAction, index = 0) {
+  const host = route.secondary ? 'secondary' : 'primary';
+  const blobPath = action === 'export' ? 'raw-blob/Pro%20message.eml?accept=message%2Frfc822' : 'same-blob/photo.png?accept=image%2Fpng';
+  expectBlobRequest(`https://${host}.example.com/download/${route.owner}/${blobPath}`, `${host}-login`, index);
+}
+
+describe('Pro blob routing', () => {
+  it.each(proRoutes.flatMap(route => proBlobActions.map(action => ({ ...route, action }))))(
+    '$label: $action uses the message owner and authenticated client', async route => {
+      const { origin, fetchMock } = await openProMessage(route, route.action);
+      await actOnProBlob(route.action);
+      await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(1));
+      expectProBlob(route, route.action);
+      if (route.owner === 'nrichmond') expect(origin.getEmail).toHaveBeenCalledWith('email', route.owner);
+    },
+  );
+
+  it.each([proRoutes[0], proRoutes[1], proRoutes[4]].flatMap(route => proBlobActions.map(action => ({ ...route, action }))))(
+    '$label: $action retains its source after account and selection changes', async route => {
+      const { a, b, fetchMock } = await openProMessage(route, route.action);
+      if (route.action === 'CID') await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(1));
+      // Leave the loaded reader mounted while a different Mail pane navigates.
+      act(() => {
+        useEmailStore.setState({ emails: [], selectedEmail: message({ id: 'other', sourceClientAccountId: 'login-primary', sourceAccountId: 'unrelated-owner' }), selectedMailbox: 'inbox', isUnifiedView: false });
+        useAuthStore.setState({ client: route.secondary ? b : a, activeAccountId: route.secondary ? 'login-other' : 'login-primary' });
+      });
+      // Switch through null, as reconnecting account switches can do.
+      act(() => useAuthStore.setState({ client: null }));
+      act(() => useAuthStore.setState({ client: route.secondary ? a : b, activeAccountId: route.secondary ? 'login-primary' : 'login-other' }));
+      await act(async () => {});
+      await actOnProBlob(route.action);
+      await waitFor(() => expect(fetchMock).toHaveBeenCalled());
+      for (let index = 0; index < fetchMock.mock.calls.length; index++) expectProBlob(route, route.action, index);
+    },
+  );
+
+  it('retains an in-flight Unified load across account and selection changes', async () => {
+    const { a, b, fetchMock } = await conversationClients();
+    let finish!: (email: Email) => void;
+    vi.spyOn(b, 'getEmail').mockImplementation(() => new Promise(resolve => { finish = resolve; }));
+    const wrongClient = vi.spyOn(a, 'getEmail');
+    useEmailStore.setState({ emails: [message({ sourceClientAccountId: 'login-other', sourceAccountId: 'nrichmond' })], selectedEmail: null, isUnifiedView: true });
+    render(<ProEmailTabBody tabId="reader" data={{ accountId: 'nrichmond', emailId: 'email', mailboxId: null, title: 'Loading' }} />);
+    await waitFor(() => expect(b.getEmail).toHaveBeenCalledWith('email', 'nrichmond'));
+    act(() => {
+      useEmailStore.setState({ emails: [], selectedEmail: message({ id: 'unrelated' }), isUnifiedView: false, selectedMailbox: 'inbox' });
+      useAuthStore.setState({ client: b, activeAccountId: 'login-other' });
+    });
+    await act(async () => finish(message({ attachments: [{ ...cardAttachment, name: 'photo.png' }] })));
+    await downloadAttachment();
+    await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(1));
+    expectProBlob(proRoutes[4], 'download');
+    expect(wrongClient).not.toHaveBeenCalled();
+    expect(b.getEmail).toHaveBeenCalledTimes(1);
+  });
+
+  it('changes CID routing when a reused reader opens identical ids on another client/owner', async () => {
+    const { a, b, fetchMock } = await conversationClients();
+    const full = inlineMessage({ attachments: [{ ...cardAttachment, name: 'photo.png', cid: 'test-image' }] });
+    vi.spyOn(a, 'getEmail').mockResolvedValue(full);
+    vi.spyOn(b, 'getEmail').mockResolvedValue({ ...full });
+    const reader = (login: string, owner: string) => <ProEmailTabBody tabId="reader" data={{ accountId: owner, clientAccountId: login, emailId: full.id, mailboxId: null, title: full.subject! }} />;
+    const { rerender } = render(reader('login-primary', 'owner-a'));
+    await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(1));
+    expectBlobRequest('https://primary.example.com/download/owner-a/same-blob/photo.png?accept=image%2Fpng', 'primary-login');
+    rerender(reader('login-other', 'owner-b'));
+    await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(2));
+    expectBlobRequest('https://secondary.example.com/download/owner-b/same-blob/photo.png?accept=image%2Fpng', 'secondary-login', 1);
+  });
+});
diff --git a/components/pro/pro-email-tab-body.tsx b/components/pro/pro-email-tab-body.tsx
index b51b900ac..88dd3d838 100644
--- a/components/pro/pro-email-tab-body.tsx
+++ b/components/pro/pro-email-tab-body.tsx
@@ -5,7 +5,7 @@ import { useTranslations } from "next-intl";
 import { EmailViewer } from "@/components/email/email-viewer";
 import { ErrorBoundary, EmailViewerErrorFallback } from "@/components/error";
 import { useAuthStore } from "@/stores/auth-store";
-import { useEmailStore } from "@/stores/email-store";
+import { useEmailStore, resolveEmailBlobContext, type EmailBlobContext } from "@/stores/email-store";
 import { useIdentityStore } from "@/stores/identity-store";
 import { useProMultiAccountIdentities } from "@/hooks/use-pro-multi-account-identities";
 import { findDraftIdentityId } from "@/lib/reply-identity";
@@ -100,6 +100,17 @@ export function ProEmailView({ emailId, client: clientOverride, accountId, onLoa
   const openComposeTabNow = useProTabStore((s) => s.openComposeTab);
 
   const [email, setEmail] = useState<Email | null>(null);
+  const [blobSource, setBlobSource] = useState<EmailBlobContext>({ client: null });
+  // A reader owns its load, including an in-flight one across account switches.
+  // Only a different message or explicit tab context starts a new load.
+  const loadRef = useRef<{
+    emailId: string;
+    clientOverride: typeof clientOverride;
+    accountId: typeof accountId;
+    blobSource: EmailBlobContext;
+    promise: Promise<Email | null>;
+    applied: boolean;
+  } | null>(null);
   const [isLoading, setIsLoading] = useState(true);
   const composerSessionIdRef = useRef(0);
 
@@ -137,11 +148,34 @@ export function ProEmailView({ emailId, client: clientOverride, accountId, onLoa
   useEffect(() => {
     let cancelled = false;
     if (!client) return;
+    let load = loadRef.current;
+    if (!load || load.emailId !== emailId || load.clientOverride !== clientOverride || load.accountId !== accountId) {
+      const state = useEmailStore.getState();
+      const ref = state.selectedEmail?.id === emailId
+        ? state.selectedEmail
+        : state.emails.find((e) => e.id === emailId);
+      // Folder/search panes supply their own context. A primary folder must
+      // not inherit an unrelated globally selected shared folder's owner.
+      const source = accountId || clientOverride
+        ? { client, accountId: accountId ?? client.getAccountId() }
+        : resolveEmailBlobContext(ref ?? null, client);
+      load = {
+        emailId, clientOverride, accountId, blobSource: source, applied: false,
+        promise: accountId || clientOverride
+          ? client.getEmail(emailId, source.accountId)
+          : fetchEmailContent(client, emailId),
+      };
+      loadRef.current = load;
+    }
+    const pending = load;
+    if (pending.applied) return;
     setIsLoading(true);
-    (accountId ? client.getEmail(emailId, accountId) : fetchEmailContent(client, emailId))
+    pending.promise
       .then((loaded) => {
         if (cancelled) return;
+        pending.applied = true;
         setEmail(loaded);
+        setBlobSource(pending.blobSource);
         if (loaded) onLoadedRef.current?.(loaded);
       })
       .catch((err) => {
@@ -153,7 +187,7 @@ export function ProEmailView({ emailId, client: clientOverride, accountId, onLoa
     return () => {
       cancelled = true;
     };
-  }, [client, emailId, accountId, fetchEmailContent]);
+  }, [client, clientOverride, emailId, accountId, fetchEmailContent]);
 
   const currentMailboxRole = useMemo(() => {
     if (!email) return undefined;
@@ -326,14 +360,15 @@ export function ProEmailView({ emailId, client: clientOverride, accountId, onLoa
     }
   }, [client, email, moveToMailbox, onClose]);
 
-  const handleDownloadAttachment = useCallback(async (blobId: string, name: string, type?: string) => {
-    if (!client) return;
+  const handleDownloadAttachment = useCallback(async (blobId: string, name: string, type?: string, _forceDownload?: boolean, source?: EmailBlobContext) => {
+    const context = source ?? blobSource;
+    if (!context.client) return;
     try {
-      await client.downloadBlob(blobId, name, type);
+      await context.client.downloadBlob(blobId, name, type, context.accountId);
     } catch (err) {
       console.error('Download failed:', err);
     }
-  }, [client]);
+  }, [blobSource]);
 
   const handleQuickReply = useCallback(async (body: string) => {
     handleReply(body);
@@ -394,6 +429,7 @@ export function ProEmailView({ emailId, client: clientOverride, accountId, onLoa
       <ErrorBoundary fallback={EmailViewerErrorFallback}>
         <EmailViewer
           email={email}
+          blobSource={blobSource}
           isLoading={isLoading}
           onReply={handleReply}
           onReplyAll={handleReplyAll}