diff --git a/lib/__tests__/timezone.test.ts b/lib/__tests__/timezone.test.ts
index 2bdc6fbd8..5fcc01f18 100644
--- a/lib/__tests__/timezone.test.ts
+++ b/lib/__tests__/timezone.test.ts
@@ -172,4 +172,12 @@ describe('mail timestamp formatting honours the override', () => {
     expect(formatDate(received)).toContain('23:00');
     expect(formatDateTime(received, '24h', { year: 'numeric', month: 'short', day: 'numeric' })).toContain('23:00');
   });
+
+  it.each(['smart', 'relative', 'full'] as const)('formatDate returns "" for an invalid date in %s mode (#1099)', (dateFormat) => {
+    useSettingsStore.setState({ timeZone: 'Asia/Tokyo', dateFormat });
+    expect(formatDate('not-a-valid-date')).toBe('');
+    expect(formatDate('10000-01-01T00:00:00Z')).toBe('');
+    expect(formatDate(new Date('nope'))).toBe('');
+    expect(formatDate(undefined as unknown as string)).toBe('');
+  });
 });
diff --git a/lib/utils.ts b/lib/utils.ts
index 67eb884c9..8262bcf25 100644
--- a/lib/utils.ts
+++ b/lib/utils.ts
@@ -96,6 +96,10 @@ function resolveDateLocale<T extends string | undefined>(
  */
 export function formatDate(date: Date | string): string {
   const d = typeof date === "string" ? new Date(date) : date;
+  // An unparsable receivedAt (e.g. a 5-digit year) makes Intl throw
+  // "RangeError: Invalid time value" and takes the whole list down with it.
+  // Leave the row's date slot blank; the viewer header shows the raw value. (#1099)
+  if (!d || Number.isNaN(d.getTime())) return "";
   const now = new Date();
 
   const locale = getEffectiveLocale();