Just install roundcube webmail for the company users. Everything works fine except when they forward their email, there is not their own email address from the from field. Is there a way to config a default identity for each user?
I guess you are talking about the email domain. Have a look at:
// This domain will be used to form e-mail addresses of new users
// Specify an array with 'host' => 'domain' values to support multiple hosts
// Supported replacement variables:
// %h - user's IMAP hostname
// %n - http hostname ($_SERVER['SERVER_NAME'])
// %d - domain (http hostname without the first part)
// %z - IMAP domain (IMAP hostname without the first part)
// For example %n = mail.domain.tld, %t = domain.tld
$config['mail_domain'] = '';
in your Roundcube config file