I'm using multiple domain in my RC

$rcmail_config['default_host'][] = 'foo.com';

$rcmail_config['default_host'][] = 'fee.com';

$rcmail_config['default_host'][] = 'fuu.com';

This creates a dropdown menu on my RC. However, users could login to these three domain. Would it be possible to set users to login only in one of these domain? I'm using MySQL and users is on local system. Basically, what I only want is if I can only user USERA to have an email of USERA@foo.com only. I tried the ff steps below:

$rcmail_config['default_host'] = 'foo.com';

And remove 

$rcmail_config['default_host'][] = 'fee.com';

$rcmail_config['default_host'][] = 'fuu.com';

Add virtuser_file.

$rcmail_config['virtuser_file'] = '/etc/mail/virtuser'; 

Contents is nelson@fee.com nelson. 

I deleted nelson on the users table of roundcubemail database.

When I tried to login using nelson and compose a message, my email in the From field is still nelson@foo.com. It should be nelson@fee.com

Am I doing the right procedure?