Setting up a CNAME record for each of the domains or subdomains that you have in a hosting account allows you to forward it to a different domain/subdomain. The forwarded Internet domain will lose all its records - A, MX and so forth, and will take the records of the domain name it's being directed to. In this light, you cannot create a CNAME record to point your domain name to a third-party company and maintain a working e-mail service with the first hosting provider. It is also very important to know that a CNAME record is always a string of words and not a number as it's frequently wrongly identified as the A record of the domain address being forwarded. One of the main uses of a CNAME record is to direct a domain name that you own through one company to the servers of some other company assuming you have set up a website with the latter. In this way, the site will appear under your own domain, not under some subdomain provided by the third-party company.