Merge pull request #680 from hildebrandttk/fix/cross-account-move

Fix/cross account move

app/(main)/[locale]/page.tsx

@@ -282,6 +282,7 @@ export default function Home() {
     toggleStar,
     setEmailKeywordsLocal,
     moveToMailbox,
+    moveToMailboxCrossAware,
     moveThreadToMailbox,
     searchEmails,
     searchQuery,
@@ -3229,7 +3230,7 @@ export default function Home() {
                 }}
                 onMoveToMailbox={async (emailId, mailboxId) => {
                   if (client) {
-                    await moveToMailbox(client, emailId, mailboxId);
+                    await moveToMailboxCrossAware(client, emailId, mailboxId);
                   }
                 }}
                 onMarkAsSpam={async (email) => {
@@ -3499,7 +3500,7 @@ export default function Home() {
                     selectedMailbox={selectedMailbox}
                     onMoveToMailbox={async (mailboxId) => {
                       if (client && selectedEmail) {
-                        await moveToMailbox(client, selectedEmail.id, mailboxId);
+                        await moveToMailboxCrossAware(client, selectedEmail.id, mailboxId);
                       }
                     }}
                     className={isMobile ? "flex-1" : undefined}

integration/tests/08-shared-moves.spec.ts

@@ -13,107 +13,154 @@ import {
 
 /**
  * Moving mail across the own-account / shared-folder boundary, in both
- * directions, and between two shared folders. The move is driven from the list
- * context menu's "Move to" submenu; the authoritative check is the server-side
- * mailbox the message ends up in, with the reliably-updating (own-account)
- * counters checked in the UI too.
+ * directions, and between two shared folders (same owner and across owners).
+ * The move is driven from the list context menu's "Move to" submenu; the
+ * authoritative check is the server-side mailbox the message ends up in.
+ *
+ * Each cross-account case asserts delivery *and* that the read state survives
+ * (Email/copy drops keywords unless carried). Removing the source, however, is
+ * currently blocked by a Stalwart bug — onSuccessDestroyOriginal destroys the
+ * copy's create-id instead of the source id, so the original is left behind
+ * (support.stalw.art #1150). Those source-removal checks are pinned test.fail
+ * until Stalwart ships the fix; same-account moves (Email/set) are unaffected.
  */
-const { alice, carol } = ACCOUNTS;
+const { alice, bob, carol } = ACCOUNTS;
 const subj = (l: string) => `IT ${l} ${Date.now()}`;
+type FolderSel = Parameters<typeof folderMailboxId>[1];
 
 test.describe('Shared-folder moves', () => {
-  let ja: JmapClient; // owner
+  let ja: JmapClient; // owner A
+  let jb: JmapClient; // owner B (cross-owner shared → shared)
   let jc: JmapClient; // grantee
   let teamA: string;
   let teamB: string;
+  let teamC: string; // owned by bob
 
   test.beforeEach(async () => {
     ja = await JmapClient.connect(alice.email, alice.password);
+    jb = await JmapClient.connect(bob.email, bob.password);
     jc = await JmapClient.connect(carol.email, carol.password);
     await ja.reset();
+    await jb.reset();
     await jc.reset();
     teamA = await ja.createSharedFolder('TeamA', carol.email);
     teamB = await ja.createSharedFolder('TeamB', carol.email);
+    teamC = await jb.createSharedFolder('TeamC', carol.email);
   });
 
-  async function seedInto(mailboxId: string, subject: string, owner = ja): Promise<void> {
-    const acct = owner === ja ? alice : carol;
+  // Seed a message into a mailbox and mark it read, so a lost $seen after the
+  // move is observable as the moved copy coming back unread.
+  async function seedRead(mailboxId: string, subject: string, owner = ja): Promise<void> {
+    const acct = owner === ja ? alice : owner === jb ? bob : carol;
     await sendMail({ from: acct.email, authPass: acct.password, to: acct.email, subject, body: 'x' });
     const m = await owner.waitForEmail(subject);
     await owner.moveEmail(m.id, mailboxId);
+    await owner.setSeen(m.id, true);
   }
 
-  test('shared folder A -> shared folder B', async ({ page }) => {
+  const seenOf = (m: any) => Boolean(m?.keywords?.$seen);
+
+  // Log in as carol, reveal the relevant shared owners, and move `subject` from
+  // `source` to `dest` via the context menu.
+  async function uiMove(
+    page: import('@playwright/test').Page,
+    opts: { subject: string; owners: string[]; source: FolderSel; dest: FolderSel },
+  ): Promise<void> {
+    await login(page, carol);
+    for (const o of opts.owners) await expandSharedFolders(page, o);
+    const destId = await folderMailboxId(page, opts.dest);
+    await openFolder(page, opts.source);
+    await forceSync(page);
+    await moveEmailTo(page, opts.subject, destId);
+    await page.waitForTimeout(2000);
+  }
+
+  const inbox: FolderSel = { role: 'inbox', shared: false };
+  const shared = (name: string): FolderSel => ({ name, shared: true });
+
+  test('shared folder A -> shared folder B (same owner)', async ({ page }) => {
     const s = subj('mv-a2b');
-    await seedInto(teamA, s);
+    await seedRead(teamA, s);
+    await uiMove(page, { subject: s, owners: [alice.email], source: shared('TeamA'), dest: shared('TeamB') });
 
-    await login(page, carol);
-    await expandSharedFolders(page, alice.email);
-    const dest = await folderMailboxId(page, { name: 'TeamB', shared: true });
-    await openFolder(page, { name: 'TeamA', shared: true });
-    await forceSync(page);
-
-    await moveEmailTo(page, s, dest);
-    await page.waitForTimeout(1500);
-
-    expect(await ja.findEmailBySubject(s, teamB), 'message in TeamB').toBeTruthy();
+    const inB = await ja.findEmailBySubject(s, teamB);
+    expect(inB, 'message in TeamB').toBeTruthy();
     expect(await ja.findEmailBySubject(s, teamA), 'message left TeamA').toBeFalsy();
+    expect(seenOf(inB), 'read state kept').toBe(true);
   });
 
-  test('shared folder B -> shared folder A', async ({ page }) => {
+  test('shared folder B -> shared folder A (same owner)', async ({ page }) => {
     const s = subj('mv-b2a');
-    await seedInto(teamB, s);
+    await seedRead(teamB, s);
+    await uiMove(page, { subject: s, owners: [alice.email], source: shared('TeamB'), dest: shared('TeamA') });
 
-    await login(page, carol);
-    await expandSharedFolders(page, alice.email);
-    const dest = await folderMailboxId(page, { name: 'TeamA', shared: true });
-    await openFolder(page, { name: 'TeamB', shared: true });
-    await forceSync(page);
-
-    await moveEmailTo(page, s, dest);
-    await page.waitForTimeout(1500);
-
-    expect(await ja.findEmailBySubject(s, teamA), 'message in TeamA').toBeTruthy();
+    const inA = await ja.findEmailBySubject(s, teamA);
+    expect(inA, 'message in TeamA').toBeTruthy();
     expect(await ja.findEmailBySubject(s, teamB), 'message left TeamB').toBeFalsy();
+    expect(seenOf(inA), 'read state kept').toBe(true);
   });
 
-  // KNOWN LIMITATION (documented via test.fail): the "Move to" submenu offers a
-  // shared folder as a destination for an own-account message, but clicking it
-  // does NOT relocate the message across the account boundary — it stays put.
-  // Same in reverse (shared -> own). If cross-account moves get implemented,
-  // these will start passing; flip them back to plain tests then.
-  test.fail('own account -> shared folder', async ({ page }) => {
+  // Cross-account cases: delivery + read state must hold (our fix); removing the
+  // source is pinned test.fail below (Stalwart #1150).
+  test('cross-owner shared -> shared: delivers and keeps read state', async ({ page }) => {
+    const s = subj('mv-a2c');
+    await seedRead(teamA, s);
+    await uiMove(page, { subject: s, owners: [alice.email, bob.email], source: shared('TeamA'), dest: shared('TeamC') });
+
+    const inC = await jb.findEmailBySubject(s, teamC);
+    expect(inC, 'message in bob TeamC').toBeTruthy();
+    expect(seenOf(inC), 'read state kept').toBe(true);
+  });
+
+  test('own account -> shared folder: delivers and keeps read state', async ({ page }) => {
     const s = subj('mv-own2sh');
     await sendMail({ from: carol.email, authPass: carol.password, to: carol.email, subject: s, body: 'x' });
-    await jc.waitForEmail(s);
+    const own = await jc.waitForEmail(s);
+    await jc.setSeen(own.id, true);
+    await uiMove(page, { subject: s, owners: [alice.email], source: inbox, dest: shared('TeamA') });
 
-    await login(page, carol);
-    await expandSharedFolders(page, alice.email);
-    const dest = await folderMailboxId(page, { name: 'TeamA', shared: true });
-    await openFolder(page, { role: 'inbox', shared: false });
-    await forceSync(page);
-
-    await moveEmailTo(page, s, dest);
-    await page.waitForTimeout(2000);
-
-    // Expected (once supported): the message moves to the owner's shared TeamA.
-    expect(await ja.findEmailBySubject(s, teamA), 'message in shared TeamA').toBeTruthy();
+    const inTeam = await ja.findEmailBySubject(s, teamA);
+    expect(inTeam, 'message in shared TeamA').toBeTruthy();
+    expect(seenOf(inTeam), 'read state kept').toBe(true);
   });
 
-  test.fail('shared folder -> own account', async ({ page }) => {
+  test('shared folder -> own account: delivers and keeps read state', async ({ page }) => {
     const s = subj('mv-sh2own');
-    await seedInto(teamA, s);
+    await seedRead(teamA, s);
+    await uiMove(page, { subject: s, owners: [alice.email], source: shared('TeamA'), dest: inbox });
 
-    await login(page, carol);
-    await expandSharedFolders(page, alice.email);
-    const dest = await folderMailboxId(page, { role: 'inbox', shared: false });
-    await openFolder(page, { name: 'TeamA', shared: true });
-    await forceSync(page);
+    const inOwn = await jc.findEmailBySubject(s);
+    expect(inOwn, 'message in own account').toBeTruthy();
+    expect(seenOf(inOwn), 'read state kept').toBe(true);
+  });
 
-    await moveEmailTo(page, s, dest);
-    await page.waitForTimeout(2000);
+  // Pinned failing: Stalwart's onSuccessDestroyOriginal leaves the original in
+  // place on a cross-account copy (support.stalw.art #1150). Un-pin once fixed
+  // upstream (our copyEmailAcrossAccounts already requests the destroy).
+  test.describe('source is removed after a cross-account move', () => {
+    test.fail(true, 'blocked by Stalwart #1150 (onSuccessDestroyOriginal destroys wrong id)');
 
-    // Expected (once supported): the message arrives in carol's own Inbox.
-    expect(await jc.findEmailBySubject(s), 'message in own account').toBeTruthy();
+    test('cross-owner shared -> shared', async ({ page }) => {
+      const s = subj('rm-a2c');
+      await seedRead(teamA, s);
+      await uiMove(page, { subject: s, owners: [alice.email, bob.email], source: shared('TeamA'), dest: shared('TeamC') });
+      expect(await ja.findEmailBySubject(s, teamA), 'original left alice TeamA').toBeFalsy();
+    });
+
+    test('own account -> shared folder', async ({ page }) => {
+      const s = subj('rm-own2sh');
+      await sendMail({ from: carol.email, authPass: carol.password, to: carol.email, subject: s, body: 'x' });
+      const own = await jc.waitForEmail(s);
+      await jc.setSeen(own.id, true);
+      await uiMove(page, { subject: s, owners: [alice.email], source: inbox, dest: shared('TeamA') });
+      expect(await jc.findEmailBySubject(s), 'original left own account').toBeFalsy();
+    });
+
+    test('shared folder -> own account', async ({ page }) => {
+      const s = subj('rm-sh2own');
+      await seedRead(teamA, s);
+      await uiMove(page, { subject: s, owners: [alice.email], source: shared('TeamA'), dest: inbox });
+      expect(await ja.findEmailBySubject(s, teamA), 'original left shared TeamA').toBeFalsy();
+    });
   });
 });

lib/demo/demo-client.ts

@@ -1094,6 +1094,7 @@ export class DemoJMAPClient implements IJMAPClient {
   // ── S/MIME raw-email helpers ──────────────────────────────────
 
   async importRawEmail(): Promise<string> { return generateDemoId('email'); }
+  async copyEmailAcrossAccounts(): Promise<string> { return generateDemoId('email'); }
   async submitEmail(): Promise<void> { /* no-op */ }
   async submitRawEmail(blob: Blob,
     identityId: string,

lib/jmap/client-interface.ts

@@ -345,4 +345,12 @@ export interface IJMAPClient {
   // ── S/MIME raw-email helpers ──────────────────────────────────
   importRawEmail(blob: Blob, mailboxIds: Record<string, boolean>, keywords?: Record<string, boolean>, accountId?: string): Promise<string>;
   submitEmail(emailId: string, identityId: string): Promise<void>;
+  /**
+   * Server-side move of one email across accounts reachable through THIS client
+   * (JMAP `Email/copy` + destroy-original). Used for delegated/shared folders,
+   * where the two accounts share a client but a client can't stage a blob in a
+   * delegated account (so the blob copy+import path doesn't work). Returns the
+   * new email id in the destination account.
+   */
+  copyEmailAcrossAccounts(emailId: string, fromAccountId: string, toAccountId: string, destMailboxId: string): Promise<string>;
 }

lib/jmap/client.ts

@@ -6394,6 +6394,43 @@ export class JMAPClient implements IJMAPClient {
    * a shared mailbox owned by another user). When omitted, falls back to the
    * client's own primary account.
    */
+  async copyEmailAcrossAccounts(
+    emailId: string,
+    fromAccountId: string,
+    toAccountId: string,
+    destMailboxId: string,
+  ): Promise<string> {
+    // Email/copy drops keywords unless the create sets them, so carry the
+    // source's over — otherwise the moved message shows up as unread.
+    const srcResp = await this.request([
+      ["Email/get", { accountId: fromAccountId, ids: [emailId], properties: ["keywords"] }, "0"],
+    ]);
+    const keywords = srcResp.methodResponses?.[0]?.[1]?.list?.[0]?.keywords ?? {};
+
+    // onSuccessDestroyOriginal is the spec-correct way to remove the source, but
+    // Stalwart currently destroys the copy's create-id instead of the source id,
+    // so the original is left behind — a duplicate on every cross-account move.
+    // Reported upstream (support.stalw.art #1150); this self-heals once fixed.
+    const response = await this.request([
+      ["Email/copy", {
+        fromAccountId,
+        accountId: toAccountId,
+        create: { c: { id: emailId, mailboxIds: { [destMailboxId]: true }, keywords } },
+        onSuccessDestroyOriginal: true,
+      }, "0"],
+    ]);
+    const res = response.methodResponses?.[0]?.[1];
+    const err = res?.notCreated?.c;
+    if (err) {
+      throw new Error(err.description || err.type || "Failed to copy email across accounts");
+    }
+    const id = res?.created?.c?.id;
+    if (!id) {
+      throw new Error("Email/copy succeeded but no ID returned");
+    }
+    return id;
+  }
+
   async importRawEmail(
     blob: Blob,
     mailboxIds: Record<string, boolean>,

stores/__tests__/email-store-cross-account-move.test.ts

@@ -0,0 +1,102 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { useEmailStore } from '../email-store';
+import type { Email, Mailbox } from '@/lib/jmap/types';
+import type { IJMAPClient } from '@/lib/jmap/client-interface';
+
+type Store = ReturnType<typeof useEmailStore.getState>;
+
+function makeMailbox(overrides: Partial<Mailbox>): Mailbox {
+  return {
+    id: 'inbox',
+    name: 'Inbox',
+    sortOrder: 0,
+    totalEmails: 0,
+    unreadEmails: 0,
+    totalThreads: 0,
+    unreadThreads: 0,
+    myRights: {
+      mayReadItems: true, mayAddItems: true, mayRemoveItems: true, maySetSeen: true,
+      maySetKeywords: true, mayCreateChild: true, mayRename: true, mayDelete: true, maySubmit: true,
+    },
+    isSubscribed: true,
+    isShared: false,
+    ...overrides,
+  };
+}
+
+function makeEmail(id: string, mailboxServerId: string): Email {
+  return {
+    id, threadId: `t-${id}`, mailboxIds: { [mailboxServerId]: true }, keywords: {},
+    size: 100, receivedAt: new Date().toISOString(),
+    from: [{ name: 'X', email: 'x@example.com' }], to: [{ name: 'Y', email: 'y@example.com' }],
+    subject: id, preview: '', hasAttachment: false, textBody: [], htmlBody: [], bodyValues: {},
+  };
+}
+
+// Own account (JMAP acct "jmap-A", reached via local account "local-A") and a
+// delegated/shared folder owned by another JMAP account ("jmap-B").
+const ownInbox = makeMailbox({ id: 'inbox-A', role: 'inbox', accountId: 'jmap-A', originalId: 'srv-inbox-A' });
+const ownArchive = makeMailbox({ id: 'archive-A', role: 'archive', accountId: 'jmap-A', originalId: 'srv-archive-A' });
+const sharedTeamA = makeMailbox({ id: 'jmap-B:srv-teamA', name: 'TeamA', accountId: 'jmap-B', originalId: 'srv-teamA', isShared: true });
+
+describe('email-store moveToMailboxCrossAware', () => {
+  let crossSpy: ReturnType<typeof vi.fn>;
+  let moveSpy: ReturnType<typeof vi.fn>;
+  const client = {} as IJMAPClient;
+
+  beforeEach(() => {
+    const email = makeEmail('e1', 'srv-inbox-A');
+    email.accountId = 'local-A';
+    crossSpy = vi.fn().mockResolvedValue(undefined);
+    moveSpy = vi.fn().mockResolvedValue(undefined);
+    useEmailStore.setState({
+      emails: [email],
+      mailboxes: [ownInbox, ownArchive, sharedTeamA],
+      selectedMailbox: 'inbox-A',
+      viewingAccountId: 'local-A',
+      isUnifiedView: false,
+      accountMailboxes: {},
+      crossAccountMoveEmails: crossSpy as unknown as Store['crossAccountMoveEmails'],
+      moveToMailbox: moveSpy as unknown as Store['moveToMailbox'],
+    });
+  });
+
+  it('routes an own → shared (cross-account) move through crossAccountMoveEmails', async () => {
+    await useEmailStore.getState().moveToMailboxCrossAware(client, 'e1', 'jmap-B:srv-teamA');
+
+    expect(moveSpy).not.toHaveBeenCalled();
+    // copy into the owner's (jmap-B) TeamA via the viewer's client, using the
+    // destination's raw server id; source is own, so no source override.
+    expect(crossSpy).toHaveBeenCalledWith(
+      new Map([['local-A', ['e1']]]),
+      'local-A',
+      'srv-teamA',
+      'jmap-B',
+      undefined,
+    );
+  });
+
+  it('routes a same-account move through the single-account moveToMailbox', async () => {
+    await useEmailStore.getState().moveToMailboxCrossAware(client, 'e1', 'archive-A');
+
+    expect(crossSpy).not.toHaveBeenCalled();
+    expect(moveSpy).toHaveBeenCalledWith(client, 'e1', 'archive-A');
+  });
+
+  it('reverse: shared → own also routes cross-account (source override set)', async () => {
+    const email = makeEmail('e2', 'srv-teamA');
+    email.accountId = 'local-A';
+    useEmailStore.setState({ emails: [email], selectedMailbox: 'jmap-B:srv-teamA' });
+
+    await useEmailStore.getState().moveToMailboxCrossAware(client, 'e2', 'inbox-A');
+
+    expect(moveSpy).not.toHaveBeenCalled();
+    expect(crossSpy).toHaveBeenCalledWith(
+      new Map([['local-A', ['e2']]]),
+      'local-A',
+      'srv-inbox-A',
+      undefined,      // dest (own) not shared
+      'jmap-B',       // source shared → override to owner account
+    );
+  });
+});

stores/email-store.ts

@@ -161,6 +161,14 @@ interface EmailStore {
   deleteEmail: (client: IJMAPClient, emailId: string, forceDelete?: boolean) => Promise<void>;
   markAsRead: (client: IJMAPClient, emailId: string, read: boolean) => Promise<void>;
   moveToMailbox: (client: IJMAPClient, emailId: string, mailboxId: string) => Promise<void>;
+  /**
+   * Move a single email, routing across the account boundary when the
+   * destination folder is owned by a different JMAP account (a delegated/shared
+   * mailbox, or a different connected account) — the "Move to" context-menu
+   * equivalent of what drag-and-drop already does. Falls back to the plain
+   * single-account `moveToMailbox` when source and destination share an account.
+   */
+  moveToMailboxCrossAware: (client: IJMAPClient, emailId: string, mailboxId: string) => Promise<void>;
   moveEmailsToMailbox: (client: IJMAPClient, emailIds: string[], mailboxId: string) => Promise<void>;
   moveThreadToMailbox: (client: IJMAPClient, emailId: string, mailboxId: string) => Promise<void>;
   /**
@@ -424,6 +432,23 @@ function resolveEmailActionContext(
   };
 }
 
+/**
+ * Local account id ("user@host") whose connected client owns `mailbox`.
+ * `mailbox.accountId` is the JMAP server's opaque id; map it back to a local
+ * client id, falling back to the viewing/active account — a delegated/shared
+ * folder has no separately-connected client, it's reached through the viewer's.
+ * Mirrors resolveDestAccountId in use-mailbox-drop.ts.
+ */
+function resolveDestLocalAccountId(mailbox: Mailbox): string | null {
+  const jmapId = mailbox.accountId;
+  if (jmapId) {
+    for (const [localId, client] of useAuthStore.getState().getAllConnectedClients()) {
+      if (client.getAccountId() === jmapId) return localId;
+    }
+  }
+  return useEmailStore.getState().viewingAccountId ?? useAuthStore.getState().activeAccountId;
+}
+
 /**
  * Builds the `UnifiedAccountClient[]` list used by every unified fan-out
  * action (browse, load-more, search). Each entry has a JMAP client plus a
@@ -1595,6 +1620,54 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
     }
   },
 
+  moveToMailboxCrossAware: async (client, emailId, destinationMailboxId) => {
+    const state = get();
+    const email = state.emails.find((e) => e.id === emailId);
+    if (!email) return;
+
+    const { mailboxes } = resolveEmailActionContext(email, client);
+    const find = (id: string) =>
+      mailboxes.find((mb) => mb.id === id) ?? state.mailboxes.find((mb) => mb.id === id);
+    const destMailbox = find(destinationMailboxId);
+    // A context-menu move acts on the visible list, so the source folder is the
+    // one currently open.
+    const sourceMailbox = find(state.selectedMailbox ?? '');
+
+    // Cross-account when the two folders live in different JMAP accounts (both
+    // own and shared mailboxes carry accountId, so this catches own↔shared too).
+    const isCrossAccount =
+      !!destMailbox &&
+      !!sourceMailbox?.accountId &&
+      !!destMailbox.accountId &&
+      sourceMailbox.accountId !== destMailbox.accountId;
+
+    if (!isCrossAccount) {
+      await get().moveToMailbox(client, emailId, destinationMailboxId);
+      return;
+    }
+
+    const destAccountId = resolveDestLocalAccountId(destMailbox!);
+    const sourceAccountId =
+      email.accountId ?? state.viewingAccountId ?? useAuthStore.getState().activeAccountId;
+    if (!destAccountId || !sourceAccountId) {
+      // Can't resolve the local endpoints — fall back rather than drop the mail.
+      await get().moveToMailbox(client, emailId, destinationMailboxId);
+      return;
+    }
+
+    // JMAP has no cross-account move: copy the raw message into the destination
+    // account's mailbox, then delete the original (crossAccountMoveEmails). The
+    // *Jmap* overrides target the owner account when a shared folder is reached
+    // through another user's client.
+    await get().crossAccountMoveEmails(
+      new Map([[sourceAccountId, [emailId]]]),
+      destAccountId,
+      destMailbox!.originalId ?? destMailbox!.id,
+      destMailbox!.isShared ? destMailbox!.accountId : undefined,
+      sourceMailbox?.isShared ? sourceMailbox.accountId : undefined,
+    );
+  },
+
   moveToMailbox: async (client, emailId, destinationMailboxId) => {
     try {
       const email = get().emails.find(e => e.id === emailId);
@@ -1763,9 +1836,23 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
         // the source clean in the happy path.
         const results = await Promise.allSettled(
           emailIds.map(async (emailId) => {
-            // When the source is a delegated/shared mailbox, the email,
-            // its blob, and the destroy all live in the owner's JMAP
-            // account, not the source client's primary one.
+            // Delegated/shared folders: one client reaches both accounts, so a
+            // server-side Email/copy moves the message. A client can't stage a
+            // blob in a *delegated* account (blobNotFound), so the blob
+            // copy+import path below is only valid across separate login
+            // clients/servers.
+            if (sourceClient === destClient) {
+              await sourceClient.copyEmailAcrossAccounts(
+                emailId,
+                sourceJmapAccountId ?? sourceClient.getAccountId(),
+                destJmapAccountId ?? destClient.getAccountId(),
+                destMailboxId,
+              );
+              return emailId;
+            }
+            // Separate clients (cross-server multi-account): the email, its
+            // blob, and the destroy all live in the owner's JMAP account, not
+            // the source client's primary one.
             const full = await sourceClient.getEmail(emailId, sourceJmapAccountId);
             if (!full?.blobId) {
               throw new Error('Source email has no raw blob to copy');