Creating a CNAME record for any of the domain names or subdomains that you have in the hosting account allows you to forward it to a different domain/subdomain. The forwarded domain will lose all its records - A, MX etc, and will take the records of the domain name it is being redirected to. In this light, you can't set up a CNAME record to point your domain name to a third-party company and keep a functional e-mail service with the first hosting company. It is also very important to know that a CNAME record is always a string of words and never a number as it's commonly wrongly identified as the A record of the domain being redirected. One of the primary uses of a CNAME record is to forward a domain which you own through one provider to the servers of some other company if you have created a website with the latter. This way, the site will appear under your own domain name, not under some subdomain provided by the third-party provider.