being asked for Secure Server details when adding email to icloud

Hi

Im trying to add my own domain email address to iCloud so that I can use it within apple mail. Ive authenticated the email addresses, but at the end it asked me to login into https://sso.secureserver.net/

But I have no idea what this is and dont have an account for it to my knowledge?! Would any body be able to explain for me? I asked for it to send the username/password to my email address - but nothing every arrives :(

many thanks

Nick