Horde is a webmail interface that you can use to view and send emails. You can use Horde to view and send emails if you have set up email accounts in your cPanel (i.e. you can’t use Horde to view/send emails for forwarding addresses).
Login to Horde
Login using your email address, e.g. emailaccount@yourdomain.com
and the password for that email account (not your cPanel password).