Creating a CNAME record for each of the domain addresses or subdomains that you have within a hosting account will permit you to forward it to a different domain/subdomain. The forwarded domain name will lose all of its records - A, MX and so forth, and will take the records of the domain name it is being directed to. In this light, you cannot create a CNAME record to forward your domain to a third-party provider and keep a working email service with the first hosting company. It is also essential to know that a CNAME record is always a string of words rather than a number as it's often mistaken for the A record of the domain name being redirected. One of the primary uses of a CNAME record is to direct a domain that you own through one company to the servers of some other company assuming you have created an Internet site with the latter. That way, the website will appear under your own domain name, not under some subdomain provided by the third-party provider.