Show receipt requested for outgoing messages

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

@@ -3978,12 +3978,16 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
         }
 
         private void onReceipt(TupleMessageEx message) {
+            if (EntityFolder.isOutgoing(message.folderType))
+                ToastEx.makeText(context, R.string.title_legend_receipt, Toast.LENGTH_LONG).show();
+            else {
                 Intent reply = new Intent(context, ActivityCompose.class)
                         .putExtra("action", "dsn")
                         .putExtra("dsn", EntityMessage.DSN_RECEIPT)
                         .putExtra("reference", message.id);
                 context.startActivity(reply);
             }
+        }
 
         private void onSearchContact(TupleMessageEx message) {
             Bundle args = new Bundle();