From 9de2efb722cf7938aff89b79fcfcb2a1ca75c310 Mon Sep 17 00:00:00 2001
From: Linus Rath <139418639+rathlinus@users.noreply.github.com>
Date: Mon, 26 Oct 2026 19:43:38 +0100
Subject: [PATCH] fix: open a shared or group account's message from its link
 instead of the own message with the same id #1351

---
 components/email/email-context-menu.tsx       |  6 +-
 components/email/email-viewer.tsx             |  4 +-
 components/mail/mail-app.tsx                  | 67 ++++++++++-------
 hooks/use-email-drag.ts                       |  4 +-
 lib/__tests__/deep-links.test.ts              | 18 +++++
 lib/deep-links.ts                             | 30 ++++++--
 lib/global-search/open-hit.ts                 |  8 ++-
 .../__tests__/email-store-link-owner.test.ts  | 71 +++++++++++++++++++
 stores/email-store.ts                         | 30 ++++++--
 9 files changed, 195 insertions(+), 43 deletions(-)
 create mode 100644 stores/__tests__/email-store-link-owner.test.ts

diff --git a/components/email/email-context-menu.tsx b/components/email/email-context-menu.tsx
index d2293ffae..0050253c4 100644
--- a/components/email/email-context-menu.tsx
+++ b/components/email/email-context-menu.tsx
@@ -3,7 +3,7 @@
 import { useMemo } from "react";
 import { useTranslations } from "next-intl";
 import { useSettingsStore } from "@/stores/settings-store";
-import { useEmailStore, removalFolder, canRemoveFromFolder } from "@/stores/email-store";
+import { useEmailStore, removalFolder, canRemoveFromFolder, emailLinkSource } from "@/stores/email-store";
 import { Email, Mailbox } from "@/lib/jmap/types";
 import {
   ContextMenu,
@@ -353,7 +353,7 @@ export function EmailContextMenu({
               icon={LinkIcon}
               label={tDeepLink("copy_message")}
               onClick={() => handleAction(() => {
-                void copyLink(buildMailPath({ mailboxId: null, emailId: email.id, threadId: null }));
+                void copyLink(buildMailPath({ mailboxId: null, emailId: email.id, threadId: null, ...emailLinkSource(email) }));
               })}
             />
             {email.threadId && (
@@ -361,7 +361,7 @@ export function EmailContextMenu({
                 icon={MessagesSquare}
                 label={tDeepLink("copy_conversation")}
                 onClick={() => handleAction(() => {
-                  void copyLink(buildMailPath({ mailboxId: null, emailId: null, threadId: email.threadId! }));
+                  void copyLink(buildMailPath({ mailboxId: null, emailId: null, threadId: email.threadId!, ...emailLinkSource(email) }));
                 })}
               />
             )}
diff --git a/components/email/email-viewer.tsx b/components/email/email-viewer.tsx
index c5bb5c58b..54a8409d6 100644
--- a/components/email/email-viewer.tsx
+++ b/components/email/email-viewer.tsx
@@ -111,7 +111,7 @@ import { useDeviceDetection } from "@/hooks/use-media-query";
 import { useIsPaneScoped } from "@/hooks/use-pane-context";
 import { useAuthStore } from "@/stores/auth-store";
 import { useAccountStore } from "@/stores/account-store";
-import { useEmailStore, resolveEmailBlobContext, emailWriteSource, type EmailBlobContext } from "@/stores/email-store";
+import { useEmailStore, resolveEmailBlobContext, emailWriteSource, emailLinkSource, type EmailBlobContext } from "@/stores/email-store";
 import { useThemeStore } from "@/stores/theme-store";
 import { EmailIdentityBadge } from "./email-identity-badge";
 import { UnsubscribeBanner } from "./unsubscribe-banner";
@@ -4461,7 +4461,7 @@ export function EmailViewer({
                 <button
                   role="menuitem"
                   onClick={() => {
-                    void copyLink(buildMailPath({ mailboxId: null, emailId: email.id, threadId: null }));
+                    void copyLink(buildMailPath({ mailboxId: null, emailId: email.id, threadId: null, ...emailLinkSource(email) }));
                     setMoreMenuOpen(false);
                     setMoreMenuSub(null);
                   }}
diff --git a/components/mail/mail-app.tsx b/components/mail/mail-app.tsx
index b4c8be3b5..c3b35909b 100644
--- a/components/mail/mail-app.tsx
+++ b/components/mail/mail-app.tsx
@@ -37,7 +37,7 @@ import type { UnifiedAccountClient } from "@/lib/unified-mailbox";
 import { connectedAccountsGrew } from "@/lib/unified-mailbox";
 import { messagePriorityFromHeaders, type MessagePriority } from "@/lib/message-priority";
 import { KeyboardShortcutsModal } from "@/components/keyboard-shortcuts-modal";
-import { useEmailStore, pendingInitialData, buildUnifiedAccountClients, invalidateUnifiedMailboxes, captureViewToken, ArchiveMailboxNotFoundError, ensureArchiveMailbox, resolveSelectedEmails, resolveUnstampedEmailAccountId, resolveEmailBlobContext, resolveEmailActionContext, emailWriteSource, type EmailBlobContext, emptyFolderMovesToTrash, bulkDeleteIsPermanent, shouldConfirmBulkDelete, isAggregateListView, removalFolder, canRemoveFromFolder } from "@/stores/email-store";
+import { useEmailStore, pendingInitialData, buildUnifiedAccountClients, invalidateUnifiedMailboxes, captureViewToken, ArchiveMailboxNotFoundError, ensureArchiveMailbox, resolveSelectedEmails, resolveUnstampedEmailAccountId, resolveEmailBlobContext, resolveEmailActionContext, emailWriteSource, emailLinkSource, type EmailBlobContext, emptyFolderMovesToTrash, bulkDeleteIsPermanent, shouldConfirmBulkDelete, isAggregateListView, removalFolder, canRemoveFromFolder } from "@/stores/email-store";
 import { findDraftIdentityIdForLogin, listRowSource, resolveDraftSource, type DraftSource } from "@/lib/draft-source";
 import { useRemoveFromFolder } from "@/hooks/use-remove-from-folder";
 import { groupSearchScopeFolders, SEARCH_SCOPE_ALL_FOLDERS } from "@/lib/search-scope-folders";
@@ -830,15 +830,23 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
 
   const buildMailUrl = useCallback((state: NavSnapshot) => {
     if (isEmbedded || proInterfaceActive) return null;
-    const path = appPath(
+    const open = useEmailStore.getState().selectedEmail;
+    const shown = open && (open.id === state.emailId || (!!state.threadId && open.threadId === state.threadId)) ? open : null;
+    // The shared account of the open message, so a reload opens it again
+    // (#1351). Not another login's: a reload must not switch the login.
+    const source = shown ? emailLinkSource(shown) : null;
+    return appPath(
       buildMailPath(
-        { mailboxId: state.mailboxId, emailId: state.emailId, threadId: state.threadId },
+        {
+          mailboxId: state.mailboxId, emailId: state.emailId, threadId: state.threadId,
+          ownerAccountId: source && !source.loginId ? source.ownerAccountId : null,
+          // Keep the marker while fullscreen is active, so reloading the dragged-out
+          // tab reopens the message fullscreen instead of in the normal layout.
+          fullscreen: fullscreenReading,
+        },
         useEmailStore.getState().mailboxes,
       ),
     );
-    // Keep the marker while fullscreen is active, so reloading the dragged-out
-    // tab reopens the message fullscreen instead of in the normal layout.
-    return fullscreenReading && state.emailId ? `${path}?view=fullscreen` : path;
   }, [isEmbedded, proInterfaceActive, fullscreenReading]);
 
   useBrowserNavigation({
@@ -1700,6 +1708,22 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
   const deepLinkHandledRef = useRef(false);
   const mailAppMountedRef = useRef(false);
   useEffect(() => { mailAppMountedRef.current = true; return () => { mailAppMountedRef.current = false; }; }, []);
+  // Point the list at a folder that actually holds a linked message, so the
+  // pane behind it shows real context and "back" lands somewhere useful.
+  const showInOwningFolder = async (activeClient: Parameters<typeof fetchEmails>[0], email: Email) => {
+    const state = useEmailStore.getState();
+    const owning = Object.keys(email.mailboxIds ?? {}).find((id) =>
+      state.mailboxes.some((mb) => mb.id === id || mb.originalId === id),
+    );
+    if (owning && owning !== state.selectedMailbox) {
+      const mailbox = state.mailboxes.find((mb) => mb.id === owning || mb.originalId === owning);
+      if (mailbox) {
+        await fetchEmails(activeClient, mailbox.id, { background: true });
+        selectMailbox(mailbox.id);
+        selectEmail(email);
+      }
+    }
+  };
   const applyMailDeepLink = async (link: MailDeepLink, opts?: { onLoad?: boolean }) => {
     // The folder list before an account switch, if one happened: until the
     // new mailbox's folders arrive the store still holds these (or nothing).
@@ -1767,8 +1791,12 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
       // In the Pro shell a message permalink opens as its own fullscreen
       // email tab - the tab body fetches the message and retitles itself.
       if (isEmbedded) {
+        // A shared account's message is fetched from that account through
+        // the active login (#1351).
+        const loginId = link.ownerAccountId ? useAuthStore.getState().activeAccountId ?? undefined : undefined;
         useProTabStore.getState().openEmailTab({
-          accountId: '',
+          accountId: link.ownerAccountId ?? '',
+          ...(loginId ? { clientAccountId: loginId } : {}),
           emailId: link.id,
           mailboxId: null,
           title: t('common.loading'),
@@ -1777,25 +1805,12 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
       }
       setLoadingEmail(true);
       try {
-        const email = await fetchEmailContent(activeClient, link.id);
+        const email = await fetchEmailContent(activeClient, link.id, link.ownerAccountId);
         if (!email) {
           toast.error(t('deep_link.message_not_found'));
           return;
         }
-        // Point the list at a folder that actually holds the message, so the
-        // pane behind it shows real context and "back" lands somewhere useful.
-        const state = useEmailStore.getState();
-        const owning = Object.keys(email.mailboxIds ?? {}).find((id) =>
-          state.mailboxes.some((mb) => mb.id === id || mb.originalId === id),
-        );
-        if (owning && owning !== state.selectedMailbox) {
-          const mailbox = state.mailboxes.find((mb) => mb.id === owning || mb.originalId === owning);
-          if (mailbox) {
-            await fetchEmails(activeClient, mailbox.id, { background: true });
-            selectMailbox(mailbox.id);
-            selectEmail(email);
-          }
-        }
+        await showInOwningFolder(activeClient, email);
         if (link.fullscreen && !isMobile) {
           // The owning-folder branch above may have skipped selecting (the
           // folder was already current) - fullscreen needs the message open.
@@ -1816,10 +1831,11 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     const openSeq = ++conversationOpenSeqRef.current;
     const source: EmailBlobContext = {
       client: activeClient, clientAccountId: useAuthStore.getState().activeAccountId ?? undefined,
+      accountId: link.ownerAccountId,
     };
     setLoadingEmail(true);
     try {
-      const threadEmails = await activeClient.getThreadEmails(link.id);
+      const threadEmails = await activeClient.getThreadEmails(link.id, link.ownerAccountId);
       if (openSeq !== conversationOpenSeqRef.current) return;
       const [group] = groupEmailsByThread(threadEmails);
       if (!group) {
@@ -1832,7 +1848,10 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
         setConversationEmails(threadEmails);
         setActiveView('viewer');
       } else {
-        await fetchEmailContent(activeClient, group.latestEmail.id);
+        const email = await fetchEmailContent(activeClient, group.latestEmail.id, link.ownerAccountId);
+        // A shared account's conversation needs its folder open: the open
+        // message is acted on in the account of the folder on screen.
+        if (email && link.ownerAccountId) await showInOwningFolder(activeClient, email);
         if (isTablet) setTabletListVisible(false);
       }
     } finally {
diff --git a/hooks/use-email-drag.ts b/hooks/use-email-drag.ts
index 33f43715d..391510827 100644
--- a/hooks/use-email-drag.ts
+++ b/hooks/use-email-drag.ts
@@ -3,7 +3,7 @@
 import { useCallback, useEffect, useMemo, useRef, DragEvent } from "react";
 import { Email } from "@/lib/jmap/types";
 import { IJMAPClient } from "@/lib/jmap/client-interface";
-import { resolveEmailBlobContext, resolveSelectedEmails, useEmailStore } from "@/stores/email-store";
+import { emailLinkSource, resolveEmailBlobContext, resolveSelectedEmails, useEmailStore } from "@/stores/email-store";
 import { emailKeyFor } from "@/lib/thread-utils";
 import { useAuthStore } from "@/stores/auth-store";
 import { useDragDropContext } from "@/contexts/drag-drop-context";
@@ -280,7 +280,7 @@ export function useEmailDrag({ email, sourceMailboxId, threadEmails }: UseEmailD
     e.dataTransfer.setData(
       "text/uri-list",
       emailsToDrag
-        .map(em => `${appUrl(buildMailPath({ mailboxId: null, emailId: em.id, threadId: null }))}?view=fullscreen`)
+        .map(em => appUrl(buildMailPath({ mailboxId: null, emailId: em.id, threadId: null, ...emailLinkSource(em), fullscreen: true })))
         .join("\r\n")
     );
 
diff --git a/lib/__tests__/deep-links.test.ts b/lib/__tests__/deep-links.test.ts
index 6743bdd46..c9696f162 100644
--- a/lib/__tests__/deep-links.test.ts
+++ b/lib/__tests__/deep-links.test.ts
@@ -242,6 +242,24 @@ describe('mail paths', () => {
     expect(link).toEqual({ kind: 'message', id: 'm1', accountId: 'acc-2' });
   });
 
+  // Email ids repeat across accounts: a link to a shared account's message
+  // names that account, or it opens the own message with the same id (#1351).
+  it('names the account owning a message or conversation outside the own one', () => {
+    const message = buildMailPath({ mailboxId: null, emailId: 'm1', threadId: null, ownerAccountId: 'cn', loginId: 'bob@x', fullscreen: true });
+    expect(message).toBe('/mail/message/m1?account=bob%40x&owner=cn&view=fullscreen');
+    const [, query] = message.split('?');
+    expect(parseMailPath(['message', 'm1'], new URLSearchParams(query))).toEqual({
+      kind: 'message', id: 'm1', accountId: 'bob@x', ownerAccountId: 'cn', fullscreen: true,
+    });
+    expect(buildMailPath({ mailboxId: null, emailId: null, threadId: 't1', ownerAccountId: 'cn' })).toBe('/mail/thread/t1?owner=cn');
+    expect(parseMailPath(['thread', 't1'], new URLSearchParams('owner=cn'))).toEqual({
+      kind: 'thread', id: 't1', accountId: undefined, ownerAccountId: 'cn',
+    });
+    // Only a message link opens fullscreen; a folder link names no owner.
+    expect(buildMailPath({ mailboxId: null, emailId: null, threadId: 't1', fullscreen: true })).toBe('/mail/thread/t1');
+    expect(buildMailPath({ mailboxId: 'c', emailId: null, threadId: null, ownerAccountId: 'cn' }, MAILBOXES)).toBe('/mail/folder/c');
+  });
+
   it('still understands the legacy ?email= notification link', () => {
     expect(parseMailPath([], new URLSearchParams('email=m9'))).toEqual({
       kind: 'message',
diff --git a/lib/deep-links.ts b/lib/deep-links.ts
index 8fa0d501c..e3c1459a4 100644
--- a/lib/deep-links.ts
+++ b/lib/deep-links.ts
@@ -137,13 +137,22 @@ const ALIASED_ROLES = new Set(['inbox', 'sent', 'drafts', 'trash', 'archive', 'j
  */
 export type MailDeepLink =
   | { kind: 'folder'; ref: string; accountId?: string; slot?: number }
-  | { kind: 'message'; id: string; accountId?: string; slot?: number; fullscreen?: boolean }
-  | { kind: 'thread'; id: string; accountId?: string; slot?: number };
+  | { kind: 'message'; id: string; accountId?: string; slot?: number; fullscreen?: boolean; ownerAccountId?: string }
+  | { kind: 'thread'; id: string; accountId?: string; slot?: number; ownerAccountId?: string };
 
 export interface MailLinkState {
   mailboxId: string | null;
   emailId: string | null;
   threadId: string | null;
+  /**
+   * The JMAP account a linked message or conversation lives in, when it is not
+   * the login's own: email ids repeat across accounts (#1351).
+   */
+  ownerAccountId?: string | null;
+  /** The login (AccountEntry.id) reaching it, when not the active one. */
+  loginId?: string | null;
+  /** Open a message link alone, without sidebar and list. */
+  fullscreen?: boolean;
 }
 
 /**
@@ -227,8 +236,16 @@ export function isFolderLinkOpen(mailboxId: string, view: OpenFolderView): boole
  * thread is what the user is looking at.
  */
 export function buildMailPath(state: MailLinkState, mailboxes: Mailbox[] = []): string {
-  if (state.threadId) return `/mail/thread/${encodeSegment(state.threadId)}`;
-  if (state.emailId) return `/mail/message/${encodeSegment(state.emailId)}`;
+  const query = (fullscreen: boolean) => {
+    const params = new URLSearchParams();
+    if (state.loginId) params.set('account', state.loginId);
+    if (state.ownerAccountId) params.set('owner', state.ownerAccountId);
+    if (fullscreen) params.set('view', 'fullscreen');
+    const qs = params.toString();
+    return qs ? `?${qs}` : '';
+  };
+  if (state.threadId) return `/mail/thread/${encodeSegment(state.threadId)}${query(false)}`;
+  if (state.emailId) return `/mail/message/${encodeSegment(state.emailId)}${query(!!state.fullscreen)}`;
   if (state.mailboxId) return `/mail/folder/${encodeSegment(buildFolderRef(state.mailboxId, mailboxes))}`;
   return '/mail';
 }
@@ -259,13 +276,14 @@ export function parseMailPath(
   // a mail dragged out into a new browser tab opens as. The Pro shell always
   // opens message links as fullscreen email tabs and ignores the flag.
   const fullscreen = search?.get('view') === 'fullscreen' || undefined;
+  const ownerAccountId = search?.get('owner') || undefined;
   const [kind, value] = segments;
 
   if (kind && value) {
     const id = decodeSegment(value);
     if (id) {
-      if (kind === 'message') return { kind: 'message', id, accountId, slot, fullscreen };
-      if (kind === 'thread') return { kind: 'thread', id, accountId, slot };
+      if (kind === 'message') return { kind: 'message', id, accountId, slot, fullscreen, ownerAccountId };
+      if (kind === 'thread') return { kind: 'thread', id, accountId, slot, ownerAccountId };
       if (kind === 'folder') return { kind: 'folder', ref: id, accountId, slot };
     }
   }
diff --git a/lib/global-search/open-hit.ts b/lib/global-search/open-hit.ts
index 6af16c54e..961fb7e36 100644
--- a/lib/global-search/open-hit.ts
+++ b/lib/global-search/open-hit.ts
@@ -95,9 +95,13 @@ export async function openHit(hit: GlobalSearchHit, options: OpenHitOptions): Pr
   // Standard layout: switch the active login when needed, then navigate.
   if (!isActiveLogin) await auth.switchAccount(hit.localAccountId);
   switch (hit.kind) {
-    case 'mail':
-      navigate?.(appPath(buildMailPath({ mailboxId: null, emailId: hit.id, threadId: null })));
+    case 'mail': {
+      // A group or shared account's hit names its account: ids repeat (#1351).
+      const own = auth.getClientForAccount(hit.localAccountId)?.getAccountId();
+      const ownerAccountId = hit.jmapAccountId && hit.jmapAccountId !== own ? hit.jmapAccountId : null;
+      navigate?.(appPath(buildMailPath({ mailboxId: null, emailId: hit.id, threadId: null, ownerAccountId })));
       return;
+    }
     case 'contacts':
       // Outside the Pro shell the store holds the active login's contacts raw.
       navigate?.(appPath(buildContactsPath({ contactId: hit.id })));
diff --git a/stores/__tests__/email-store-link-owner.test.ts b/stores/__tests__/email-store-link-owner.test.ts
new file mode 100644
index 000000000..ce063e51d
--- /dev/null
+++ b/stores/__tests__/email-store-link-owner.test.ts
@@ -0,0 +1,71 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { emailLinkSource, useEmailStore } from '../email-store';
+import { useAuthStore } from '../auth-store';
+import type { Email, Mailbox } from '@/lib/jmap/types';
+import type { IJMAPClient } from '@/lib/jmap/client-interface';
+
+// Email ids repeat across accounts (Stalwart numbers each account's mail the
+// same way). A message link only named the id, so a link to a shared or group
+// account's message opened the own message with that id (#1351).
+
+const row = (id: string, mailboxId: string): Email => ({
+  id, threadId: `t-${id}`, mailboxIds: { [mailboxId]: true }, keywords: {}, subject: `Subject ${id}`,
+  receivedAt: '2026-10-01T00:00:00Z', from: [], to: [], preview: '', size: 1, hasAttachment: false,
+} as Email);
+
+const mailbox = (id: string, extra: Partial<Mailbox> = {}): Mailbox => ({
+  id, originalId: id, name: id, role: null, accountId: 'own', totalEmails: 1, unreadEmails: 0,
+  totalThreads: 1, unreadThreads: 0, sortOrder: 0, isSubscribed: true, myRights: {}, ...extra,
+} as unknown as Mailbox);
+
+const OWN_INBOX = mailbox('inbox', { role: 'inbox' });
+const GROUP_INBOX = mailbox('grp:inbox', { originalId: 'inbox', role: 'inbox', accountId: 'grp', isShared: true });
+
+function client() {
+  return {
+    getAccountId: () => 'own',
+    getEmail: vi.fn(async (id: string, accountId?: string) => row(id, accountId ? `${accountId}:inbox` : 'inbox')),
+  } as unknown as IJMAPClient & { getEmail: ReturnType<typeof vi.fn> };
+}
+
+describe('message links and the account that owns the message', () => {
+  let c: ReturnType<typeof client>;
+  beforeEach(() => {
+    c = client();
+    useAuthStore.setState({ client: c, activeAccountId: 'alice@example.org' } as never);
+    useEmailStore.setState({
+      mailboxes: [OWN_INBOX, GROUP_INBOX],
+      accountMailboxes: {},
+      viewingAccountId: null,
+      selectedMailbox: 'inbox',
+      selectedEmail: null,
+      emails: [row('e1', 'inbox')],
+      searchQuery: '',
+    });
+  });
+
+  it('fetches a linked message from the account the link names, not the own row with its id', async () => {
+    const email = await useEmailStore.getState().fetchEmailContent(c, 'e1', 'grp');
+    expect(c.getEmail).toHaveBeenCalledWith('e1', 'grp');
+    expect(email?.mailboxIds).toEqual({ 'grp:inbox': true });
+  });
+
+  it('fetches from the listed row\'s account without an owner', async () => {
+    await useEmailStore.getState().fetchEmailContent(c, 'e1');
+    expect(c.getEmail).toHaveBeenCalledWith('e1', undefined);
+  });
+
+  it('names the owner of a row in a shared folder, and none for the own one', () => {
+    expect(emailLinkSource(row('e1', 'inbox'))).toEqual({ ownerAccountId: null, loginId: null });
+    useEmailStore.setState({ selectedMailbox: 'grp:inbox' });
+    expect(emailLinkSource(row('e1', 'grp:inbox'))).toEqual({ ownerAccountId: 'grp', loginId: null });
+  });
+
+  it('names the account and login a stamped row of a merged view comes from', () => {
+    const fromBob = { ...row('e1', 'inbox'), sourceClientAccountId: 'bob@example.org', sourceAccountId: 'b1' };
+    const bobClient = { getAccountId: () => 'b1' };
+    useAuthStore.setState({ getClientForAccount: (id: string) => (id === 'bob@example.org' ? bobClient : null) } as never);
+    expect(emailLinkSource(fromBob)).toEqual({ ownerAccountId: null, loginId: 'bob@example.org' });
+    expect(emailLinkSource({ ...fromBob, sourceAccountId: 'b-grp' })).toEqual({ ownerAccountId: 'b-grp', loginId: 'bob@example.org' });
+  });
+});
diff --git a/stores/email-store.ts b/stores/email-store.ts
index fb5583209..26fb6f145 100644
--- a/stores/email-store.ts
+++ b/stores/email-store.ts
@@ -335,7 +335,8 @@ interface EmailStore {
   // times; later calls are no-ops while a prior one is in flight.
   prefetchInitialData: (client: IJMAPClient) => Promise<void>;
   loadMoreEmails: (client: IJMAPClient) => Promise<void>;
-  fetchEmailContent: (client: IJMAPClient, emailId: string) => Promise<Email | null>;
+  /** `ownerAccountId`: the JMAP account a link names for the message (#1351). */
+  fetchEmailContent: (client: IJMAPClient, emailId: string, ownerAccountId?: string) => Promise<Email | null>;
   fetchQuota: (client: IJMAPClient) => Promise<void>;
   sendEmail: (client: IJMAPClient, to: string[], subject: string, body: string, cc?: string[], bcc?: string[], identityId?: string, fromEmail?: string, draftId?: string, fromName?: string, htmlBody?: string, attachments?: Array<{ blobId: string; name: string; type: string; size: number; disposition?: 'attachment' | 'inline'; cid?: string }>, inReplyTo?: string[], references?: string[], delayedUntil?: string, envelopeMailFrom?: string, options?: { requestReadReceipt?: boolean; requestDsn?: boolean; requireTls?: boolean; priority?: MessagePriority; localAccountId?: string; draftAccountId?: string }) => Promise<SendEmailResult>;
   sendRawEmail: (client: IJMAPClient, rawMimeBlob: Blob, identityId: string, delayedUntil?: string, envelopeRecipients?: string[]) => Promise<SendEmailResult>;
@@ -1235,6 +1236,20 @@ export function emailWriteSource(email: Pick<Email, 'sourceClientAccountId' | 's
   return { clientAccountId, accountId };
 }
 
+/**
+ * What a link to a row in the view on screen names besides its id, as ids
+ * repeat across accounts and logins (#1351): the JMAP account when it is not
+ * the login's own, the login when it is not the active one.
+ */
+export function emailLinkSource(email: Pick<Email, 'sourceClientAccountId' | 'sourceAccountId'>): { ownerAccountId: string | null; loginId: string | null } {
+  const auth = useAuthStore.getState();
+  const { client, accountId, clientAccountId } = resolveEmailBlobContext(email, auth.client);
+  return {
+    ownerAccountId: accountId && accountId !== client?.getAccountId() ? accountId : null,
+    loginId: clientAccountId && clientAccountId !== auth.activeAccountId ? clientAccountId : null,
+  };
+}
+
 // List requests can finish after navigation. Never apply an old folder/tag
 // response (or error) to the view the user has since selected.
 /**
@@ -3831,15 +3846,22 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
     }
   },
 
-  fetchEmailContent: async (client, emailId) => {
+  fetchEmailContent: async (client, emailId, ownerAccountId) => {
     try {
       // Route to the owning account. In aggregate views (All Mail, unified,
       // cross-account) the selected mailbox is virtual, so derive the client +
       // accountId from the email itself (handles shared/group accounts); fall
       // back to the selected-mailbox shared-folder logic for normal views.
       const selected = get().selectedEmail;
-      const listEmail = selected?.id === emailId ? selected : get().emails.find(e => e.id === emailId);
-      const { client: actionClient, accountId } = resolveEmailBlobContext(listEmail ?? null, client);
+      let listEmail = selected?.id === emailId ? selected : get().emails.find(e => e.id === emailId);
+      let { client: actionClient, accountId } = resolveEmailBlobContext(listEmail ?? null, client);
+      // A link names the account of a message outside the login's own; a
+      // listed row with its id from another account is not that message.
+      if (ownerAccountId && accountId !== ownerAccountId) {
+        listEmail = undefined;
+        actionClient = client;
+        accountId = ownerAccountId;
+      }
       if (!actionClient) throw new Error('No connected client for email source');
 
       const email = await actionClient.getEmail(emailId, accountId);