Fixes #4084 - Mail user cant delete created mail forwarding

interface/web/mailuser/form/mail_user_cc.tform.php

@@ -69,7 +69,9 @@ $form["tabs"]['mailuser'] = array (
 					'type' => 'TOLOWER')
 			),
 			'validators' => array (
-				0 => array ( 'type' => 'ISEMAIL', 'errmsg'=> 'cc_error_isemail'),
+				0 => array ( 'type' => 'REGEX', 
+					'regex' => '/^(\w+[\w\.\-\+]*\w{0,}@\w+[\w.-]*\.[a-z\-]{2,10}){0,1}(,\s*\w+[\w\.\-\+]*\w{0,}@\w+[\w.-]*\.[a-z\-]{2,10}){0,}$/i',
+					'errmsg'=> 'cc_error_isemail'),
 			),
 			'default' => '',
 			'value'  => '',