diff --git a/components/email/__tests__/calendar-invitation-banner.test.tsx b/components/email/__tests__/calendar-invitation-banner.test.tsx
index 37d9be2d5..efef720a8 100644
--- a/components/email/__tests__/calendar-invitation-banner.test.tsx
+++ b/components/email/__tests__/calendar-invitation-banner.test.tsx
@@ -23,6 +23,7 @@ const mocks = vi.hoisted(() => {
   const authState = {
     client: clientMock,
     primaryIdentity: { email: 'user@example.com' },
+    identities: [{ email: 'user@example.com' }] as Array<{ email: string }>,
     getClientForAccount: vi.fn((id: string) => (id === 'login-b' ? sourceClientMock : undefined)),
   };
 
@@ -188,6 +189,7 @@ describe('CalendarInvitationBanner', () => {
     mocks.sourceClientMock.fetchBlob.mockReset();
     mocks.sourceClientMock.fetchBlob.mockRejectedValue(new Error('no blob'));
     mocks.authState.getClientForAccount.mockClear();
+    mocks.authState.identities = [{ email: 'user@example.com' }];
     mocks.emailState.viewingAccountId = null;
     mocks.emailState.selectedMailbox = 'inbox';
     mocks.emailState.mailboxes = [];
@@ -546,6 +548,41 @@ describe('CalendarInvitationBanner', () => {
     expect(await screen.findByText('Response sent')).toBeInTheDocument();
   });
 
+  it('finds the user under an alias identity the invite was sent to (#1283)', async () => {
+    mocks.authState.identities = [{ email: 'user@example.com' }, { email: 'Alias@example.com' }];
+    const participants = {
+      aliasAttendee: {
+        '@type': 'Participant',
+        email: 'alias@example.com',
+        name: 'User',
+        roles: { attendee: true },
+        participationStatus: 'needs-action',
+      },
+    };
+    mocks.calendarState.events = [
+      { id: 'event-8', uid: 'uid-8', start: '2026-03-30T09:00:00Z', participants },
+    ];
+    mocks.clientMock.parseCalendarEvents.mockResolvedValue([
+      { uid: 'uid-8', title: 'Alias Event', start: '2026-03-30T09:00:00Z', participants },
+    ]);
+    mocks.calendarState.rsvpEvent.mockResolvedValue(true);
+
+    render(<CalendarInvitationBanner email={makeEmail({ id: 'email-8' })} />);
+
+    fireEvent.click(await screen.findByText('Accept'));
+
+    await waitFor(() => {
+      expect(mocks.calendarState.rsvpEvent).toHaveBeenCalledWith(
+        mocks.clientMock,
+        'event-8',
+        'aliasAttendee',
+        'accepted',
+        null,
+      );
+    });
+    expect(await screen.findByText('Response sent')).toBeInTheDocument();
+  });
+
   it('says nothing was sent when a plugin stops the answer', async () => {
     mocks.calendarState.events = [
       {
diff --git a/components/email/calendar-invitation-banner.tsx b/components/email/calendar-invitation-banner.tsx
index cbc1a18b2..53919235a 100644
--- a/components/email/calendar-invitation-banner.tsx
+++ b/components/email/calendar-invitation-banner.tsx
@@ -34,7 +34,7 @@ import {
   getInvitationTrustAssessment,
   formatEventSummary,
   formatInvitationSchedule,
-  findParticipantByEmail,
+  findParticipantByEmails,
   extractMethodFromRawIcs,
   type EventSummary,
   type InvitationMethod,
@@ -390,7 +390,14 @@ export function CalendarInvitationBanner({ email }: CalendarInvitationBannerProp
   const viewedMailbox = viewMailboxes.find((m) => m.id === selectedMailboxId);
   const sharedOwnerAccountId = viewedMailbox?.isShared ? viewedMailbox.accountId : undefined;
   const blobAccountId = email.sourceAccountId ?? sharedOwnerAccountId ?? parseClient?.getAccountId();
-  const currentUserEmail = useAuthStore((s) => s.primaryIdentity?.email);
+  // Every address the user sends as, primary first: an invite may be
+  // addressed to an alias identity (#1283).
+  const identityEmails = useAuthStore(useShallow((s) => {
+    const emails = [s.primaryIdentity?.email, ...s.identities.map((identity) => identity.email)]
+      .filter((address): address is string => Boolean(address))
+      .map((address) => address.toLowerCase());
+    return Array.from(new Set(emails));
+  }));
   const calendarInvitationParsingEnabled = useSettingsStore((s) => s.calendarInvitationParsingEnabled);
   const timeFormat = useSettingsStore((s) => s.timeFormat);
   const { calendars, supportsCalendar, importEvents, rsvpEvent, updateEvent, events: storeEvents, setSelectedDate } = useCalendarStore(useShallow((state) => ({
@@ -524,12 +531,12 @@ export function CalendarInvitationBanner({ email }: CalendarInvitationBannerProp
     ? storeEvents.find((e) => e.uid === parsedEvent.uid)
     : null;
 
-  const currentUserParticipant = existingEvent && currentUserEmail
-    ? findParticipantByEmail(existingEvent, currentUserEmail)
+  const currentUserParticipant = existingEvent
+    ? findParticipantByEmails(existingEvent, identityEmails)
     : null;
 
-  const fallbackParsedParticipant = !currentUserParticipant && parsedEvent && currentUserEmail
-    ? findParticipantByEmail(parsedEvent, currentUserEmail)
+  const fallbackParsedParticipant = !currentUserParticipant && parsedEvent
+    ? findParticipantByEmails(parsedEvent, identityEmails)
     : null;
 
   const participantForUser = currentUserParticipant || fallbackParsedParticipant;
@@ -545,9 +552,8 @@ export function CalendarInvitationBanner({ email }: CalendarInvitationBannerProp
     || myParticipant?.participant.participationStatus
     || null;
   const userIsOrganizer = Boolean(isOnlyOrganizer);
-  const userIsSender = Boolean(
-    currentUserEmail && email.from?.[0]?.email?.toLowerCase() === currentUserEmail.toLowerCase()
-  );
+  const senderAddress = email.from?.[0]?.email?.toLowerCase();
+  const userIsSender = Boolean(senderAddress && identityEmails.includes(senderAddress));
   const bannerTitle = getBannerTitle(t, method);
   const bannerInfo = getBannerInfo(t, method, userIsOrganizer, supportsCalendar);
   const trustAssessment = parsedEvent && !userIsSender ? getInvitationTrustAssessment(parsedEvent, email, method) : null;
@@ -602,8 +608,8 @@ export function CalendarInvitationBanner({ email }: CalendarInvitationBannerProp
       const eventForRsvp = existingEvent
         ? await resolveExistingEventForRsvp()
         : null;
-      const existingEventParticipant = eventForRsvp && currentUserEmail
-        ? findParticipantByEmail(eventForRsvp, currentUserEmail)
+      const existingEventParticipant = eventForRsvp
+        ? findParticipantByEmails(eventForRsvp, identityEmails)
         : null;
       const canFallbackToParsedParticipant = Boolean(
         existingEvent
@@ -646,7 +652,7 @@ export function CalendarInvitationBanner({ email }: CalendarInvitationBannerProp
             (e) => e.uid === parsedEvent.uid
           );
           const participant = myParticipant
-            || (newEvent && currentUserEmail ? findParticipantByEmail(newEvent, currentUserEmail) : null);
+            || (newEvent ? findParticipantByEmails(newEvent, identityEmails) : null);
           if (newEvent && participant) {
             if (!(await rsvpEvent(client, newEvent.id, participant.id, status, replyToForRsvp))) return;
             setRsvpStatus(status);
diff --git a/lib/calendar-invitation.ts b/lib/calendar-invitation.ts
index a467068b4..2ff7a22ea 100644
--- a/lib/calendar-invitation.ts
+++ b/lib/calendar-invitation.ts
@@ -702,6 +702,22 @@ export function formatInvitationSchedule(
   return range.end ? `${start} – ${formatPoint(range.end, true)}` : start;
 }
 
+/**
+ * The participant matching the first of `emails` found in the event. The
+ * user's identities, primary first: an invite may be addressed to an alias
+ * identity rather than the primary address (#1283).
+ */
+export function findParticipantByEmails(
+  event: Partial<CalendarEvent>,
+  emails: readonly string[]
+): { id: string; participant: CalendarParticipant } | null {
+  for (const email of emails) {
+    const found = findParticipantByEmail(event, email);
+    if (found) return found;
+  }
+  return null;
+}
+
 export function findParticipantByEmail(
   event: Partial<CalendarEvent>,
   email: string