Apparently the smtp user and password were missing from the config.inc.php file in Roundcube 1.3.4, resulting in a
[code]Relay access denied[/code] when trying to send mail from Roundcube.
Adding
[code]
$config[‘smtp_user’] = ‘%u’;
$config[‘smtp_pass’] = ‘%p’;
[/code]
to config/config.inc.php solved the problem.