diff --git a/stores/__tests__/settings-store-sync.test.ts b/stores/__tests__/settings-store-sync.test.ts
index 0a0ad153a..671179a15 100644
--- a/stores/__tests__/settings-store-sync.test.ts
+++ b/stores/__tests__/settings-store-sync.test.ts
@@ -52,20 +52,41 @@ describe('settings sync debounce', () => {
     });
   });
 
-  it('defaults the signature auto-insert toggles and the separator to off, and exports all three', () => {
+  it('defaults the signature auto-insert toggles to on and exports them', () => {
     const settings = useSettingsStore.getState();
-    expect(settings.signatureNewMailEnabled).toBe(false);
-    expect(settings.signatureReplyForwardEnabled).toBe(false);
+    expect(settings.signatureNewMailEnabled).toBe(true);
+    expect(settings.signatureReplyForwardEnabled).toBe(true);
     expect(settings.signatureSeparatorEnabled).toBe(false);
 
     const exported = JSON.parse(settings.exportSettings()) as Record<string, unknown>;
     expect(exported).toMatchObject({
-      signatureNewMailEnabled: false,
-      signatureReplyForwardEnabled: false,
+      signatureNewMailEnabled: true,
+      signatureReplyForwardEnabled: true,
       signatureSeparatorEnabled: false,
     });
   });
 
+  it('keeps inserting the signature for users whose saved settings predate the toggles', async () => {
+    useSettingsStore.getState().resetToDefaults();
+    // Saved by a build without the toggles: the keys are missing.
+    localStorage.setItem('settings-storage', JSON.stringify({
+      state: { signaturePosition: 'below_quote', signatureSeparatorEnabled: true },
+      version: 12,
+    }));
+    await useSettingsStore.persist.rehydrate();
+    expect(useSettingsStore.getState().signatureNewMailEnabled).toBe(true);
+    expect(useSettingsStore.getState().signatureReplyForwardEnabled).toBe(true);
+
+    // A server copy written by such a build has no toggles either.
+    useSettingsStore.getState().importSettings(
+      JSON.stringify({ signaturePosition: 'above_quote' }),
+      { serverAccountId: 'a@example.com' },
+    );
+    expect(useSettingsStore.getState().signatureNewMailEnabled).toBe(true);
+    expect(useSettingsStore.getState().signatureReplyForwardEnabled).toBe(true);
+    localStorage.removeItem('settings-storage');
+  });
+
   it('does not rewrite a pending account snapshot after another account becomes active', async () => {
     const settings = useSettingsStore.getState();
     settings.enableSync('a@example.com', 'https://mail-a.example.com');
diff --git a/stores/settings-store.ts b/stores/settings-store.ts
index 56b69fa93..fa5cd60aa 100644
--- a/stores/settings-store.ts
+++ b/stores/settings-store.ts
@@ -932,8 +932,10 @@ const DEFAULT_SETTINGS = {
   subAddressDelimiter: DEFAULT_SUB_ADDRESS_DELIMITER,
   sendDelaySeconds: 0 as SendDelaySeconds,
   signaturePosition: 'below_quote' as SignaturePosition,
-  signatureNewMailEnabled: false,
-  signatureReplyForwardEnabled: false,
+  // On, as before the toggles existed: saved settings and server copies
+  // from older builds lack these keys and fall back to this default.
+  signatureNewMailEnabled: true,
+  signatureReplyForwardEnabled: true,
   signatureSeparatorEnabled: false,
   signatureDetails: EMPTY_SIGNATURE_DETAILS,
   requestReadReceiptDefault: false,