diff --git a/components/calendar/calendar-app.tsx b/components/calendar/calendar-app.tsx
index 215ca19d7..b9eba1af4 100644
--- a/components/calendar/calendar-app.tsx
+++ b/components/calendar/calendar-app.tsx
@@ -15,10 +15,10 @@ import { useEmailStore } from "@/stores/email-store";
 import { useSettingsStore } from "@/stores/settings-store";
 import { useIdentityStore } from "@/stores/identity-store";
 import { useAccountStore } from "@/stores/account-store";
-import { useAccountSecurityStore } from "@/stores/account-security-store";
 import { usePolicyStore } from "@/stores/policy-store";
 import { toast } from "@/stores/toast-store";
 import { useIsDesktop, useIsMobile } from "@/hooks/use-media-query";
+import { useAccountPrincipalEmails } from "@/hooks/use-account-principal-emails";
 import { Button } from "@/components/ui/button";
 import { CalendarToolbar } from "@/components/calendar/calendar-toolbar";
 import { CalendarMonthView } from "@/components/calendar/calendar-month-view";
@@ -130,17 +130,9 @@ export function CalendarApp({ linkSegments }: CalendarAppProps = {}) {
   const contacts = useContactStore((s) => s.contacts);
   const normalizedViewMode = isCalendarViewMode(viewMode) ? viewMode : "month";
 
-  // Aliases live on the principal, not on identities; fetch them so an
-  // alias-organized event is recognised as the user's own (see isOrganizer).
-  const accountEmails = useAccountSecurityStore((s) => s.emails);
-  const fetchPrincipal = useAccountSecurityStore((s) => s.fetchPrincipal);
-  const principalFetchedRef = useRef(false);
-  useEffect(() => {
-    if (principalFetchedRef.current) return;
-    principalFetchedRef.current = true;
-    if (accountEmails.length > 0) return; // already loaded elsewhere
-    void fetchPrincipal();
-  }, [accountEmails, fetchPrincipal]);
+  // Aliases live on the principal, not on identities; the calendar needs them
+  // so an alias-organized event is recognised as the user's own (see isOrganizer).
+  const accountEmails = useAccountPrincipalEmails(client);
 
   // The default ParticipantIdentity (draft-ietf-jmap-calendars §6) is the
   // address new invitations are organised from, so it goes first: the event
diff --git a/hooks/__tests__/use-account-principal-emails.test.tsx b/hooks/__tests__/use-account-principal-emails.test.tsx
new file mode 100644
index 000000000..f98c96a8e
--- /dev/null
+++ b/hooks/__tests__/use-account-principal-emails.test.tsx
@@ -0,0 +1,56 @@
+import { render, act, cleanup } from '@testing-library/react';
+import { describe, it, expect, beforeEach, afterEach, vi, type Mock } from 'vitest';
+import { useAccountPrincipalEmails } from '../use-account-principal-emails';
+import { useAccountSecurityStore } from '@/stores/account-security-store';
+import type { IJMAPClient } from '@/lib/jmap/client-interface';
+
+// The calendar needs the principal's alias addresses to recognise an
+// alias-organised event as the user's own. The JMAP client is restored
+// asynchronously after a page load, so the fetch has to wait for it: firing
+// on mount failed with "Not authenticated", and the once-only guard then
+// never retried for the rest of the session.
+
+let seen: string[] = [];
+
+function Harness({ client }: { client: IJMAPClient | null }) {
+  seen = useAccountPrincipalEmails(client);
+  return null;
+}
+
+const client = {} as IJMAPClient;
+let fetchPrincipal: Mock<() => Promise<void>>;
+
+beforeEach(() => {
+  seen = [];
+  fetchPrincipal = vi.fn<() => Promise<void>>().mockResolvedValue(undefined);
+  useAccountSecurityStore.setState({ emails: [], fetchPrincipal });
+});
+
+afterEach(cleanup);
+
+describe('useAccountPrincipalEmails', () => {
+  it('waits for the JMAP client instead of failing on mount', () => {
+    const { rerender } = render(<Harness client={null} />);
+    expect(fetchPrincipal).not.toHaveBeenCalled();
+
+    rerender(<Harness client={client} />);
+    expect(fetchPrincipal).toHaveBeenCalledTimes(1);
+  });
+
+  it('fetches once per mount, not on every render or store update', () => {
+    const { rerender } = render(<Harness client={client} />);
+    rerender(<Harness client={client} />);
+    act(() => {
+      useAccountSecurityStore.setState({ emails: ['me@example.com', 'alias@example.com'] });
+    });
+    expect(fetchPrincipal).toHaveBeenCalledTimes(1);
+    expect(seen).toEqual(['me@example.com', 'alias@example.com']);
+  });
+
+  it('skips the fetch when the principal is already loaded elsewhere', () => {
+    useAccountSecurityStore.setState({ emails: ['me@example.com'] });
+    render(<Harness client={client} />);
+    expect(fetchPrincipal).not.toHaveBeenCalled();
+    expect(seen).toEqual(['me@example.com']);
+  });
+});
diff --git a/hooks/use-account-principal-emails.ts b/hooks/use-account-principal-emails.ts
new file mode 100644
index 000000000..62a734c68
--- /dev/null
+++ b/hooks/use-account-principal-emails.ts
@@ -0,0 +1,29 @@
+import { useEffect, useRef } from 'react';
+import type { IJMAPClient } from '@/lib/jmap/client-interface';
+import { useAccountSecurityStore } from '@/stores/account-security-store';
+
+/**
+ * The account's principal addresses - its primary address plus the enabled
+ * aliases - loaded on first use. Aliases live on the Stalwart principal, not
+ * on the identities, so a view that must recognise an alias-organised event
+ * as the user's own (the calendar's isOrganizer) needs this list.
+ *
+ * The fetch waits for the JMAP client. After a page load the client is
+ * restored asynchronously; asking for the principal before it exists only
+ * fails with "Not authenticated", and a once-only guard that fires on mount
+ * then blocks the retry for the rest of the session.
+ */
+export function useAccountPrincipalEmails(client: IJMAPClient | null): string[] {
+  const emails = useAccountSecurityStore((s) => s.emails);
+  const fetchPrincipal = useAccountSecurityStore((s) => s.fetchPrincipal);
+  const fetchedRef = useRef(false);
+
+  useEffect(() => {
+    if (!client || fetchedRef.current) return;
+    fetchedRef.current = true;
+    if (emails.length > 0) return; // already loaded elsewhere
+    void fetchPrincipal();
+  }, [client, emails, fetchPrincipal]);
+
+  return emails;
+}