roundcubemail/plugins/additional_message_headers/config.inc.php.dist

<?php

// $config['additional_message_headers']['X-Remote-Browser'] = $_SERVER['HTTP_USER_AGENT'];
// $config['additional_message_headers']['X-Originating-IP'] = $_SERVER['REMOTE_ADDR'];
// $config['additional_message_headers']['X-RoundCube-Server'] = $_SERVER['SERVER_ADDR'];

// if( isset( $_SERVER['MACHINE_NAME'] )) {
//     $config['additional_message_headers']['X-RoundCube-Server'] .= ' (' . $_SERVER['MACHINE_NAME'] . ')';
// }

// To remove (e.g. X-Sender) message header use null value
// $config['additional_message_headers']['X-Sender'] = null;

?>