Fix: add Return-Path for simplemail class for used the "error" mail or "form" mail to avoid feedback at www-data

htdocs/includes/simplemail/class.mail.php

@@ -11,6 +11,7 @@ class simplemail {
 
 	var $Xsender;
 	var $ErrorsTo;
+	var $returnpath;
 	var $XMailer = 'PHP';
 	var $XPriority = 3;