Rules is a pro feature

app/src/main/java/eu/faircode/email/FragmentRules.java

@@ -279,6 +279,11 @@ public class FragmentRules extends FragmentBase {
     }
 
     private void onMenuExport() {
+        if (!ActivityBilling.isPro(getContext())) {
+            startActivity(new Intent(getContext(), ActivityBilling.class));
+            return;
+        }
+
         Intent intent = new Intent(Intent.ACTION_CREATE_DOCUMENT);
         intent.addCategory(Intent.CATEGORY_OPENABLE);
         intent.setType("*/*");