Multiserver Setup

I am following the
ISPConfig 3.1 Manual
to install a (3.2 Multiserver Setup) ( web, mail, db, ns1, ns2) however I am missing the part about installing the mail client ( roundcube) can somebody confirm this? where do I install roundcube?

 

If the mailserver has no webserver, install it on the webserver and adjust the rouncube-config to connect to the mailserver

 

I know I'm supposed to install it on the ( mail) server, just making sure. I don't want to break anything

If I install roundcube on the "mail " server, do I need to make any other settings on the main web server?

 

the ispconfit 3.1 manual needs updating, It doesn't reflect the current version of ispconfig 3.1

 

You can install roundcube on the webserver and set
$config['default_host'] = 'mailserver';
$config['smtp_server'] = 'mailserver';
$config['smtp_user'] = '%u';
$config['smtp_pass'] = '%p';