I'm free user and I want to display a custom login url, I have already added CNAME record mail.mydomain.com to business.zoho.com; but when I try to access with my custom url I have this message: 

Curiously in private window in chrome the custom login url is working fine; I read that I have to put the custom login or subdomain in Domains section in Dashboard or Control Panel, in my case is mail.cifepconsulting.com; but as I'm free user I can't add more than 1 domain here.

Please help me to make this custom url work, explain me what I have to do.

Thank you very much.