Login - "Server" field will not autofill

[oregonmac7]

I've successfully installed RoundCube and it's working on my website. However, one thing is not:

When you get to the login page for WebMail there are three fields: 'Username', 'Password', and 'Server'. I want Server to be automatically assigned.

I've followed the instructions and done this:
$rcmail_config['default_host'] = 'localhost';

My config file even looks just like this, but the 'Server' field is still showing up and is still unpopulated. What do I do to make this work?

Thanks for any and all help.

Best regards,
Lee in Oregon