Creating a CNAME record for any of the domains or subdomains that you've got in the hosting account allows you to direct it to a different domain/subdomain. The forwarded Internet domain will lose all of its records - A, MX and so on, and will take the records of the Internet domain it's being directed to. In this light, you can't create a CNAME record to forward your domain to a third-party company and keep a working email service with the first hosting company. It is also important to note that a CNAME record is always a string of words and not a number as it is commonly wrongly identified as the A record of the domain address being forwarded. One of the major uses of a CNAME record is to point a domain which you own through one provider to the servers of another provider assuming you have created a site with the latter. This way, the Internet site will appear under your own domain address, not under some subdomain provided by the third-party company.