Troubles with Dovecot + Webmin on Debian 6.0
To use roundcube and shown as [email protected], you should login roundcube with your full email address [email protected]. If you forget to do so, it will append the full machine name.
Update
In roundcube config, setup the following
$rcmail_config['username_domain'] = '<the-domain-name>';
Go through your webmin interface and learn how to put it in. There is webmin module for roundcube.