No Secure Login HTTPS (ssl) on ZOHO Mail Custom Login URL...

No Secure Login HTTPS (ssl) on ZOHO Mail Custom Login URL...

I have setup a Custom Login URL for my ZOHO email account with my domain "mail.mydomain.com"... But I noticed that this Custom URL does not come up as an SSL secure site ( https://)...   It comes up as just a plain http:// site...  However.. After I enter in my email address and password it does convert over to SSL " https://mail.zoho.com/zm/#mail/inbox "...  Shouldn't the custom login page also be a secure SSL site to protect login credential...?

If I use the standard ZOHO mal login url " www.zoho.com/mail/login.html "  it will come up an SSL secure site " https://www.zoho.com/mail/login.html "...

Is there a way to make my Custom Login URL " mail.mydomain.com " an SSL https:// Secure Login Site...?