Creating a CNAME record for each of the domains or subdomains that you've got within a hosting account will enable you to forward it to a different domain/subdomain. The forwarded domain address will lose all its records - A, MX etc, and will take the records of the domain address it's being redirected to. In this light, you simply can't create a CNAME record to direct your domain name to a third-party provider and maintain a functional email service with the first hosting provider. It is also essential to know that a CNAME record is always a string of words and never a number as it is generally wrongly identified as the A record of the domain name being forwarded. One of the main uses of a CNAME record is to forward a domain you own through one company to the servers of another provider if you have set up a site with the latter. By doing this, the site will appear under your own domain name, not under some subdomain provided by the third-party provider.