Issue :
Problem sending email via roundcube on a server with :
Centos 4 i386
11.24.4-STABLE_35075
Fix :
Try the following :
vi /usr/local/cpanel/base/3rdparty/roundcube/config/main.inc.php
and change
$rcmail_config[‘smtp_user’] = ‘%u’;
to
$rcmail_config[‘smtp_user’] = ”;
This should fix the issue !