Creating a CNAME record for any of the domain addresses or subdomains that you have in a hosting account will permit you to point 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 it's being pointed to. In this light, you cannot create a CNAME record to point your domain to a third-party company and keep a working e-mail service with the first provider. It is also very important to know that a CNAME record is always a string of words rather than a number as it's generally mistaken for the A record of the domain being redirected. One of the major uses of a CNAME record is to forward a domain address that you own through one provider to the servers of another provider assuming you have created a website with the latter. In this way, the website will appear under your own domain, not under some subdomain provided by the third-party provider.