diff --git a/src/lib/syncobjects/syncobject.php b/src/lib/syncobjects/syncobject.php
index 9b9edee6..db86ea80 100644
--- a/src/lib/syncobjects/syncobject.php
+++ b/src/lib/syncobjects/syncobject.php
@@ -580,6 +580,8 @@ public function Check($logAsDebug = false) {
                         $output = array();
                         foreach ($mails as $mail) {
                             if (! Utils::CheckEmail($mail)) {
+                                ZLog::Write(LOGLEVEL_WARN, sprintf(" email=%s, @=%s, undiscoled-recipients=%s", $email, (strpos($email, '@') !== false),  ($email === "undisclosed-recipients:;") ));
+
                                 ZLog::Write(LOGLEVEL_WARN, sprintf("SyncObject->Check(): object from type %s: parameter '%s' contains an invalid email address '%s'. Address is removed.", $objClass, $v[self::STREAMER_VAR], $mail));
                             }
                             else